Adventure Locations and Ideas (DnD Other)
From D&D Wiki
- 1 Introduction
- 2 Cities
- 3 Fortifications
- 3.1 Mighty citadel
- 3.2 Abandoned castle
- 3.3 Wizard's tower
- 3.4 Wilderness keep
- 3.5 Choke points and bottle necks
- 4 Religious locations
- 5 Wilderness
- 5.1 Enchanted forest
- 5.2 Vast desert
- 5.3 Wide ocean
- 5.4 Raging volcano
- 5.5 Magic island
- 5.6 Swamp
- 5.7 Goblin valley
- 5.8 Tundra
- 5.9 Fertile grasslands
- 5.10 Savannah
- 5.11 Giant mountains
- 5.12 Exotic jungle
- 5.13 Dragon's lair
- 6 The Underdark
- 6.1 Vision
- 6.2 Noise
- 6.3 Air
- 6.4 Water
- 6.5 Terrain
- 6.6 Geology
- 6.7 Ecology
- 6.8 Doors, bottlenecks and fortifications
Below are a selected number of ideas for places to adventure in, complete with explanations and adventure hooks. Some areas, usually the more sophisticated ones, have more detailed explanations than others. Obviously, the only limits to where one can adventure in a fantasy role-playing game are set by one's imagination, and these settings should be considered no more than a tiny fraction of what the mind can conceive. Below, there are mentioned a number of general fantasy settings, both archetypal and stereotypical alike, and any variant on them can be and ought to be considered.
City settings operate on a different basis than most other locations. In a city, there are usually laws and authorities, and the very dynamics of life are greatly different than in the countryside; the pace is quicker, the street are crowded, the buildings are larger, and the concentrations of great wealth and great poverty are more pronounced. Urban adventures generally take place over less area than those set elsewhere, and are usually done in the context of a set government and society. The most important thing to remember about a city is that it is artificial, not natural; the kinds of foes one tends to face in urban areas are products of civilization, not nature.
Of course, the size of a city can mean little to defining it, if there is some special attribute that it has. Epithets such as "the city of dragons" or "the city of gold" are useful in constituting an urban area's character.
A relatively small urban area, this city has not yet reached its full potential, but, given favorable conditions, shall do so one day. Expect to see a growing population, increasingly wealthy citizens, and new construction in this setting. The greatest problems a city such as this might face are the struggles against nature, having to push back the wilderness in order to settle more people.
- Two brothers who have founded the city fight over its rulership.
- The city's expansion has displaced native creatures which now threaten the urban area.
- A migrating tribe of orcs threatens the city.
- New settlers have disturbed a major entity of the woods when they cleared new land.
- A neighboring settlement has declared war on the city.
At this stage of development, the city and its institutions are fully developed and the population is rather large. Its merchants are rich, its temples are huge, and its cultural, economic, and political influence is felt both regionally and worldwide. The major problems facing the city are internal. Power struggles, crime, and inequality are the major dilemmas. At this point, the city's government is generally competent and clean, and is usually trying to fix the problem rather than be the cause of it. Adventures are likely to focus on preventing problems before they happen.
- Two rich merchants fight over a rare and valuable artifact.
- There are suspicions of a plot against the rulers of the city.
- A great and powerful act of sabotage is planned, to destroy the city walls and leave it vulnerable to an attack.
- An evil organisation plans to weaken the city by unleashing a plague upon it's citizens.
- Wizards from a rival nation bombard the city with devastating results.
A city whose laws, economy, population, institutions, or all of the above is in decline. If this state of being should come to pass, the city's former glory is fading, and although not fully gone, shows clear signs of decline. Corruption, recession, plague, and population loss are all characteristic of the urban area. The schemes players try to stop have usually already begun.
- Laws banning necromancy have been lifted and attacks by undead are being reported in great numbers.
- Rumors say that demon cults are behind a series of recent disappearances.
- The water supply has been mysteriously cut off and people are forced to flee the drought.
- Mass "cleansing" of minority races, in defiance of the laws, have begun.
- For years, the sea lanes which connected the city to the world have been cut off by sea monsters, and business is drying up.
A city that has fallen under the influence of dark powers is considered fallen. In a sense, it is the opposite of the great city; rather than be an agent for justice, the city is under control of a tyrant whose word is law, or has else fallen under the control of evil magics, devils, wicked dragons, malevolent wizards, or some other power. Rebel forces are common, and good adventurers in the city may be interested in helping them. Alternatively, the fallen city may be in a state of lawlessness, and the streets could be ruled by bands of thugs and criminals. Evil plans have already succeeded, and so players may be involved in helping to change the situation.
- An ancient dragon has forced his way onto the throne of the city, and rules it for his own enrichment, imposing crushing taxes.
- The slum-dwelling poor are revolting against the corrupted king.
- Evil clerics in charge of the city plan to kill off half of the city's population as a blood sacrifice.
- Anarchy has reigned ever since the last regent died off without an heir.
- An evil vizier has usurped the throne and plans to summon a great evil.
Ruins occur in one of two main ways; the physical destruction of the settlement they were a part of, or the undermining of the social, economic, religious, or political systems which supported them. Likely to be the home of monsters and the undead.
- A dragon has made its home in the crumbling remains of the treasury, and just getting to the lair may be a challenge due to the ruins.
- A magical artifact still lies within ruins, but navigating the broken remains of the buildings is a dangerous task.
Below are some ideas to work with when designing your fortifications for your game. For dungeon masters who are short on time, there's a nice page to generate random castles quickly [here].
A towering building that is built to outlast siege. It may be in the center of a city or on an imposing, defensible location like a clifftop or on an island in a lake. It could be tough and intimidating, or a place of great beauty. Typically, citadels have their own water supply, plausibly a stairwell all the way down to a cistern at ground water level, rainwater collectors or a fresh water spring. When siege threatens, cattle and grain supplies are brought inside. The walls are built like the layers of an onion, forcing would-be attackers through easily defendable bottle necks. When things go bad, defenders can retreat behind raised bridges and portcullises, to the next level of the citadel. Citadels have safe rooms and secret escape tunnels underground. Airborne assailants may be fended off by spiked roofs with nowhere to land, conventional ranged weapons, flying defenders, and magic such as gusts of wind, air-gas mixtures that lower aerodynamic lift, fire wards, bolts of lightning, deathly clouds or flying swarms of summoned monsters.
- An unnamed citadel's lord hires a group of experts, to improve his citadel's defenses. Products and services could include but not be limited to
- piles of rocks to throw or launch
- boiling oil or tar
- gargoyles and golems
- long range weapons
- self-sustaining acres or livestock, inexhaustible water supply
- troop training, specialized personnel
- moats, wall improvements, battlements, fences and barbed wire
- watch towers with continual spotlights
- extra dungeons and interrogation rooms to isolate and eliminate dissidents from within
- various magical defense mechanisms
- abjuration magic against different types of damage
- divination magic against scrying, cloaked, disguised or invisible infiltrators
- traps that deal different types of damage
- teleporters to reinforcements or as an escape route for the nobles
- recharging healing stations
- food and water purification
- doors with identification locks that are monitored centrally and can be opened, closed, locked and unlocked remotely. When used without the proper authorization, silent alarms go off and automated traps activate.
- a map of the castle depicting the location of all mandatory identification tattoos
- floating, invisible eyes to monitor key locations or suspicious behavior. These eyes may or may not carry death rays.
- Of course, all of these come at varying costs, depending on the financial solvability of the employer. Offered solutions come with a maintenance contract and a guarantee of always working 50% of the time. Change requests are optional but expensive. Prices exclude write-off of used equipment, work hours, meetings, communication and management fees, transport costs, unforeseen hindrances, acts of Gods and fringe benefits. All-in solutions also take into account the optimization of the castle's staff and inventory management.
- An unnamed citadel's lord needs to dispose of the designers who know the secrets of the castle's defenses, not to mention they are a horrible financial drain. Double cross these villainous designers in the name of the law, or expose the untrustworthy lord and destabilize the region.
Perfectly good castles don't get abandoned for no reason. The defenses might have been compromised by siege. A disease or curse might have driven away or eliminated the occupants. Some major geologic event might have made the castle uninhabitable, like unstable ground, a redirected river, a nearby looming volcano or infertile surrounding countryside.
- This castle has been abandoned for far too many years and undead stalk the halls.
- A castle hasn't been abandoned at all. The inhabitants withdrew into recluse, and silence anyone that's a witness to the contrary.
- All castles along the river, one after another, are being destroyed by an unknown cataclysmic event. Everyone except the staff has fled before it is too late.
- The enemy has conquered the surrounding lands, cutting of supply lines. Before abandoning it, the castle has been elaborately trapped.
- The chaplain seems to have fallen out of favor with his deity. The divine being he summoned did not take the error in his ways lightly and has corrupted his mortal form. The inhabitants of the castle fled in horror as a fate worse than death might befall them as well. Now the kingdom needs someone to atone for the chaplain's sins and right his wrongs, in order to gain the deity's favor once again, and reclaim the castle that holds a key position in the kingdom's border defenses. This is a perfect opportunity for some ambitious adventurers to move up in life.
- For some reason, this castle has continuously been attacked by invisible stalkers. Astrologers have linked the start of the attack, with a certain celestial event years ago.
- You are fleeing from a superior force of raiders (human bandits, orc platoon, hordes of goblins, vanguard of an enemy army..). Your pursuers are relentlessly tracking you, and night is falling. It's likely they will catch up to you when you need to rest. Maybe you could make your way to that ruin where your party spent the previous night, and entrench yourself. Individual party members need to apply their specialized skill set to fortify the ruins as best you can. There is little time left. If they want you, let it cost them dearly.
The tower of a mighty wizard, protected by great magics. How common wizard's towers are, depends a lot on the setting, and how prevalent magic is. It is a recurring theme that wizards want to have the biggest possible towers, which has been suggested is a male trait.
Considering how dangerous magic can be, there will probably be a lot more towers from wizards that aren't really as mighty as perceived by the populace. With a high risk of death, there are many beginning wizards that build towers, but only a few live to be mighty. Of course, the very mightiest of wizards will probably inhabit towers that are world famous, and there aren't too many of those around.
Wizard's towers are tricky to implement well in a game. Make them too powerful, and they'll be hard to fit into the setting without disrupting it entirely. Make them not powerful enough, and they won't be worth investigating.
This isn't exactly a tower that's inhabited by a wizard. It's a defensive tower that was built by, or upgraded by a mighty wizard. These could be located at borders, city walls, keeps and citadels, strategically located at a river confluence, at a mountain pass, overseeing a lake or large underground cavern.
- Infiltrate an enemy watchtower as a spy. Map the building, inventorize the defenses, relay the information back to your contractor without having your cover blown.
- We have received vital information about the defenses of a watchtower. Replace the watchmen discreetly and await further orders.
- Investigate a watchtower that has been unresponsive. The teleport sigil to the tower is not working either. It could just be a failure of the stationed guard detachment. But it could be an omen to a full scale invasion.
Stationary base of operations
Beginning mages usually claim a dungeon or ruin, or have a modest dwelling constructed. Here they can study in peace and quiet, conduct their research, make a beginning with a laboratory, experiment with their very first magical items, start acquiring their own library, keep some familiars, and so on.
It could be a good idea to occupy a tower in a secluded area, so as not to antagonize any population centers with potentially dangerous experiments, and conveniently avoiding prying eyes. Suitable locations are in a swamp, on the other side of the mountain range, at the bottom of the ocean.
A wizard's tower is an appealing target for thieves. Adventurers soon learn to covet magical items and weapons, libraries full of arcane knowledge, spell books lying around, fully equipped laboratories complete with ingredients. This means that any wizard worth his might, will have to defend his tediously expanded inventory from hypothetical intruders. The home of a wizard will probably be highly dangerous to roam around in, or even approach uninvited.
When a wizard moves up on the mighty scale, he might find it hard to leave his first tower behind after investing so much effort into it. When important quests force him to travel, the tower could be made remotely accessible, such as by teleport, wormhole or dimension door.
- While travelling along a swamp, you can see a sinister crooked tower looming over the fog. When you navigate your way painstakingly slow to the mysterious tower, you are confronted by several mud men. Arriving at the soggy island on which stands the dark tower, a homunculus or imp with a deadly sting attacks you before retreating back to the roof. Behind the tower is a grave marked by a mossy stone post. There doesn't seem to be anyone around. Is the tower abandoned or might the occupant(s) come back any time? The interior is guarded by a beholder. The 2nd level basement has a well and uncountable spiders that seem to be hiding everywhere, 1 level down is a huge library that shouldn't fit under this swampy mound, a workshop on the ground floor has tens of unique little monster figurines. Upstairs is a strange contraption pointing out the window and a large four-poster bed that looks supernaturally comfortable and inviting...
- This ruin is too accessible. You'll need to do another humiliating mission for those demanding dwarves, in exchange for thorough repairs of the outer walls and gate.
- Dwarves are just too expensive for an aspiring wizard that needs his hard earned copper pieces. Research how to summon some servants to rebuild the damn walls.
- Summoning creatures every few hours is a huge drain on your magical resources that are desperately needed for research. Better raise some skeletons for repetitive chores. Now, where can one acquire corpses?
- A wizened old lady has been helping you out with teaching you some magic, after you saved her cat from climbing up an ent. Now she aids you in constructing the wormhole that will allow you to travel back to your tower in the blink of an eye. As a favor in return, she asks you to retrieve a bag of holding for her. When you enter your new wormhole with the bag of holding, to return to your homely tower, the fabric of space-time rips and you end up somewhere in limbo. The voice of the old lady booms ominously "AAHAAAHAAAAAA .. MORTAL FOOL !! EONS WE HAVE WAITED TO FIND A WAY INTO YOUR WORLD !!!"
Mobile base of operations
A wizard might want to take his well equipped base with him, but doing so requires the expenditure of quite a bit of magical energy. Examples of relocatable towers are towers that propel themselves with legs, or bury through the earth like a purple worm, towers on floating rocks or clouds, towers that are located in another dimension.
- Find some storm giants, and steal their cloud technology without getting killed in the process.
- You find an obscure document in a far-away corner of this library, outlining the construction of a magical crystal ball, that can exchange its interior with a spherical volume of your choice that is 10.000 times larger. You could even shrink your tower into it and carry it around, only to extract it somewhere else at a time of your choosing.
When a wizard envisions his tower to be a center where people flock to, his tower is likely stationary, lest people are able to find it. His tower may be an expression of his might, towering high into the clouds. Or it could be a shop for adventurers to upgrade their gear, or identify or sell any interesting trinkets they come across while dungeon delving. It could be a public library, or a school where aspiring mages can receive training.
- Spells are cheaper for members of the local mages guild. Enroll in the guild, to gain access to the library tower. Gain status by running an occasional errand, retrieving hard-to-come-by magical items, and doing other quests for the guild.
When magic goes wrong, disaster follows. Be wary of abandoned towers. Deadly levels of magic might be leaking. Signs to watch for are spontaneously formed golems like mud men, whirling clouds of whatever material is available, spells that are disrupted, weird spatial manifestations, sounds that don't seem quite right, mutated or unnaturally large animals, the list goes on..
When magic isn't cast exactly right, it disrupts reality in unforeseen ways and may rip the fabric of space-time, opening a doorway to ancient horrors into this dimension, demons, extra dimensional entities, you name it.
- The lab of the city's waste disposal has exploded. Someone needs to fight his way through giant sow bugs, millipedes, raggamoffyns, carrion crawlers, oozes, fungi, and garbage men ghosts, and put a plug in the radiation leak. The city has vacancies for a team of innovative garbage men.
Originally just a fence to keep livestock inside at night, and predators outside. Fences were replaced by a log palisade, possibly surrounded by an earthen wall and / or ditch. The walls sometimes include one or two watchtowers which are situated to view the outside of the walls. Keeps strategically have their own water supply, such as a spring or a well. Housing inside may consist of tents, barracks built in the walls, a separate main building or even a cave in the cliff side against which the keep was built.
- The keep is occupied by the enemy. Infiltrate and poison the well. Make sure all their spawn and whores are dead too.
- Livestock is found dead in the morning, completely drained of blood. Find a way to defend the keep against flying monsters. Or is one of the inhabitants a vampire? Time is of the issue, there are only two sheep left.
- A local warlord is not happy that the keep is not paying tribute. Actually he wants the place for himself. Logistics are being sabotaged, shepherds threatened, wounded or killed, crops and fields destroyed.. Help the keep eradicate the nuisance once and for all.
Choke points and bottle necks
Certain locations are better suited to control traffic through an area than others. Border forts see a lot of action against enemy scouts, smugglers and monsters, keeping the troops well trained. Meanwhile, in the capital, everything is peaceful and the bureaucrats like to keep it that way, dulling the wits of the military with every political stalling manoeuvre. The border fiefs are left to their own, growing strong and independent from the central kingdom.
Below are some examples where local warlords could have reinforced their position, although more are possible. A dungeon master is encouraged to look at the map of his or her particular setting, and identify plausible locations where an imperial nation (or his players' characters) would consolidate their power.
These usually have a bastion or tower on each side, with seriously reinforced gates or portcullises. Consider that any nearby fords will probably be guarded too.
- After paying the toll, the party of adventurers is allowed to cross, and is suddenly locked in between the opposing gatehouses. Archers appear on the battlements. Demands are shouted unnaturally loud. Disarm, step away from the horses and cart, lie on the bridge face down and wait to be taken into custody, or die. As the wizard starts casting defensive spells, she curses under her breath. Magicks don't seem to be working properly. Unarmored adventurers might try leaping into the water, leaving all their gear behind.
Mountain pass gate
This is a perfect location to tax travelers into a kingdom. Certain goods are forbidden contraband. A smart commanding officer might profit from price differences between both sides of the border.
- Adventurers are hired to escort collected tithes that are sent to the royal palace. However, this small treasure is only a fraction of the true income which the mountain pass collects, and is only meant to appease the king's court. The adventurers get wind of what's going on, involving them in political intrigue between the royalty, the mountain pass garrison and possibly the bordering country. For which purposes does the mountain pass bolster its power? Is this enough reason to keep the mountain pass's secret and become accomplices? The players might want to help them grow stronger. The players could use their knowledge as leverage against the garrison's commander, to further their own goals. Or maybe the players decide the garrison's command needs to be replaced by someone more competent, who can find a better use for the illegal revenue. The kingdom might be in serious need of the extra income, which it is missing out on.
Valley road fort
A castle that sends out knights to check on anyone who travels through their valley.
River confluence tower
A tower that overlooks a confluence of two rivers. Ships not flying allied banners are shot at with artillery-like ranged weapons and fireballs.
River mouth lighthouse
A lighthouse may have a dual function. On one side it serves to guide merchant ships that are out at sea, to the river mouth and the trade ports upriver. On the other hand, it sends warning overland to the nearest upriver city when sea monsters or hostile fleets navigate upstream.
A road that only surfaces when it is low tide. The road towards the island is lined with poles.
- The rocky cliffs all around an island make it impossible to reach by boat, making the tidal road its only access route. At the island, the road leads to a portcullis gate house.
A stair to the entrance of a huge cave, which could be a well guarded entrance to the Underdark, a holy pilgrimage, a defensible location for a noble's palace...
- A breathtakingly impressive stairway is divided in several terraces or tiers, which each hold an entire castle. The magnificent palace at the top is dwarfed by the enormous cave looming beyond.
While it doesn't literally have to be a temple (it can be a church, cathedral, etc.), great religious structures have been built by races all over the world in order to accommodate a large population.
- An ancient monster, sealed beneath the temple is beginning to stir, and must be defeated before it escapes and unleashes its full might.
- The Temple of Zilchus, God of commerce, stands in the middle of the town square, market stalls competing for space between the pillars of the outside gallery. This place has got a lot of tithes flowing in. It can't all be used to keep the trade routes safe. Can it?
Various religions have places that are especially important to them. A healing shrine, the site of a major relic, and the tomb of a holy man would all, among other things, qualify as such a place. Pilgrims and clerics alike can be found in abundance at these places, and the irreplaceable nature of the site makes it especially valuable.
- A sacred icon has been stolen in the middle of the night.
- Enemies of the religion plot to destroy the sanctuary, to spread panic, fear and despair. The adventurers must uncover the plot and save the day.
- In a beautiful clearing, deep in this ancient forest, lies a large stone slab with several iron rings embedded on all sides. This is where this year's virgins reach womanhood all solstice night long. All hail Beory of the Old Faith.
Unlike a public sanctuary, the monasteries of the world are intentionally closed off to prevent outsiders from interrupting the lives of quiet reflection and passive meditation contained within.
- A traitorous monk plans to overthrow the grandmaster.
- A long-lost tome of deadly magic is found in an abbey.
- Abbeys of Zuoken are known to train superb fighting monks. Although the monks have helped fight off war on occasion, the local government cannot abide their independent political stance anymore. A rogue army of super fighters right in the middle of the kingdom is unacceptable. Join the siege to destroy the unlawful monks, infiltrate the abbey to learn their secrets (and sell them to the highest bidder), or help the monks avert destruction.
Not all religious sites stay sanctified forever. Some places are abandoned over time, only to be rediscovered by dark forces. In the case of ancient burial sites, it is not unheard of for dark cultists, such as those of Orcus, to take over and turn the site from a place of eternal rest into one of unnatural horror.
- Two brothers interrupt the sleep of a dead tyrant who unleashes his forces across the region.
- The doors to this ruined church seem to be inscribed with the holy symbol of Nerull the Reaper. Inside you find scores of skeletons lying around, including one that's slouched over a scythe that nails a beautiful naked young woman to the altar.
Despite their holy nature, not all temples and holy sites are immune to evil. Corruption, schism, heresy, fanaticism, apostasy, atheism, and conversion have all led followers of various religions to abandon their faith, and often fall into a dark path. Sometimes, this leads a religious site to be converted from its original form into a wicked place, where practices which may be antithetical to the original faith that it was built by are performed.
- An ancient water nymph has been forgotten, as the people from the village take their fresh water for granted. Now the water has been making people ill. Check out the mad old fart's claims that the lady of the water is punishing the village for their sacrilege.
- The Tree of Fertility has gone missing. Seriously?
- A crazed dwarf keeps the candles burning 24/7 in his self made shrine to Pelor of The Light, mumbling with bulging blood shot eyes about the coming of the Ur-Dark. When did this beardy fellow last sleep? Whoops, what a freak gust of wind?! WHAT THE? Stop screaming already!! And w-why is it g-g-getting s-so ef-ef-effing c-c-cold-d all of a s-sud-den?
These places are dedicated to a deity, be it a well known God, or a more obscure divine being, perhaps a nature spirit or animistic concept, sometimes a saint. People may officially adhere to the state religion, while secretly praying to a multitude of demi-gods or idols.
- A local wishing well holds thousands of silver coins. Find a way to distract the hordes of pious fanatics, grab the loot, and get away with it!
- In the middle of the fields between two farmsteads, stands a small chapel to Istus, lady of our fate. The old spinster that has been maintaining the chapel her entire life, has had a suspicious series of good luck. The mayor is looking for some investigators to determine if she can be taxed more.
- Believers say that Hextor's six armed statue comes to life once every 100 years. It grants his strongest follower a black gauntlet that holds six arrows, which supposedly allows the wearer to dominate and rule an entire nation. Time to eradicate every last wannabe weakling pilgrim that hopes to win that gauntlet.
- Why does some lunatic hermit wizard scare all prying eyes away from his cave? Is he simply trying to achieve some sense of divinity, by isolating himself to solitary confinement? Is he keeping some valuable magic items for himself? Might he be guarding a ritualistic offering site from being used ever again? Nah, treasure probably.
The largest category for adventures for most parties, the wilds are a product of the natural patterns of the ecosystem and geology. Forces of nature, both natural and supernatural pose challenges to those who defy them, and sentient settlement, if any, is limited in scope.
A wood infused with the magic of life itself, an enchanted forest could contain creatures such as elves, centaurs, satyrs, nymphs, unicorns, pegasi, minotaurs, harpies, wolves, bears, and many others. Magic here is raw, wild, and untamed, and any number of spirits and ancient primal powers might be hidden within. The trees are likely to be gigantic ancient plants that let little light shine through to the forest floor, and some may be weird and magical.
It could be a sea of shifting sand dunes or a rocky wasteland. Whatever it looks like, water and food is hard to come by and only the toughest plants, creatures and people can survive.
- Bandits are attacking the merchant trails that transport much needed supplies across the desert!
- An evil being is controlling the water supply of a desert settlement, effectively holding the citizens to ransom. He must be stopped!
An expanse of water that stretches on beyond the horizon. Occasional islands are hidden. Adventurers may need to sail the seas, facing pirates, storms and sea monsters. Even with water breathing spells its depths cannot be fully explored, due to crushing pressure and freezing, dark trenches.
- A map says that a great treasure is hidden in a dungeon. The problem is, it's on an island far out to sea, so getting there will be a problem...
- Pirates have been attacking ships, killing the crews and then carrying off valuable cargoes, and now a party of adventurers has been hired to provide security for an important shipment.
- Sink or capture the ships of a competing "merchant fleet" out on the open water, where no-one can witness it. Acquire a letter of marque from a nation of your choice, to strengthen the nation's naval influence in these parts, while legalizing any
piracyunlicensed adventuring on your part.
- Sea monsters have developed a taste for sailors, and so heroes must put them off their meals. Permanently.
- Every year, during the longest night, an island supporting a seaweed covered ruin, rises from the water under the sign of Yeathan, God of drowning, aquatic calamities, watery death and dark water.
- Track down and capture a water elemental to upgrade your ship with a jet stream engine.
- Capture a vital fresh water source along a naval route. Deny drinking water to enemy political factions, while forging bonds with allied nations. Demand exorbitant prices. Expect the powers that be to strike back.
It's big, it's bad, and you probably shouldn't get near it if you don't have an immunity to fire. Volcanoes can unleash lava flows, ash clouds, toxic gasses, earthquakes and lumps of hot rock. Any beings that dwell in it would most likely be fiery creatures like fire elementals and red dragons. However, volcanic ash does make fertile soil, so expect a few villages in the area who don't mind tempting fate.
- The only way to destroy a cursed artifact is to cast it into a volcano. (As long as you group doesn't mind this LOTR idea!)
- A villain has used magical power to unleash the power of the volcano upon his enemies/innocent villagers!
- The lair of an evil villain is located within the heart of the fire mountain itself, because who doesn't want a volcano base?
The home of strange creatures and powerful magic, isolated from the mainland. The island could be in the middle of an ocean, lake or sea, or just off the coast. It's a very good place to hide something important. Island inhabitants are hostile to any outsiders that don't understand their archaic measurement system. They are proficient seafarers and fishermen. The conspicuous likeness in their paranoid facial expressions shows centuries of inbreeding.
- There's some dark secret the islanders all know about, but keep silent about at all costs. Strangers who find out too much of the horrible truth disappear without trace.
- Your boat has been sabotaged. Someone doesn't want you to leave.
- The island has an abundance of some local product, while direly lacking in some others. In addition, the exchange rate of silver to gold differs from the mainland. Set up a naval trade route. Profit!
- The rocky coastline is littered with washed up shipwrecks. A local sailor tells a tall tale of mermaids who lure sex-craved crews onto the cliffs to eat the drowning victims. Beach combers have recovered merely a fraction of the cargo these ships carried, but no-one dares go into the water to search for more.
- When an eerie foghorn sounds from far out at sea, all islanders lock up their homes and close the window shutters.
It's wet, it's full of bugs that won't let the wizard sleep, and you just know there's danger lurking under the surface. Creatures like lizardfolk, oozes, slimes, jellies, snakes, crocodiles, giant frogs, carnivorous fish, acid squirting giant snails, leeches, and millions of mosquitoes dwell in swamps. Dangers may include slimy, disease filled waters and mud that can suck you down to a sticky end, or flammable swamp gas. Will-o-wisps point the way to safe havens. Hags and witches shun society and make their homes near or in swamps. Even the twisted and gnarled plants are out to eat you. Also, trolls.
- Lizard people are hiding in the depths of the swamp, raiding villages. Their camp is concealed by the thick plant life and there are no safe trails to get there.
- Suddenly, your blood seems to diffuse through your skin and into the perpetual mist around you.
- Did you know that every chopped off part of troll, regenerates to become an entirely new troll? So why didn't trolls overrun the entire Realm, ages ago? Well, they need water to regenerate. Also, trolls are cannibals; the smaller ones get mercilessly hunted by the larger ones. How big can trolls become? There haven't been any reliable eye witnesses who could tell the tale or write it down. Anyways, this is your chance to find out.
- You need to get a sample of an extremely poisonous eel that lives only in this godforsaken bog. The reward would better be worth it.
- Looming in the fog, a skeleton of some huge monster is partly showing above the surface.
- The players are sucked into the swamp at some point which acts like a portal to another world.
The home of goblins. There are likely to be thick forests that conceal their homes and allow them to ambush trespassers. The goblins might farm in the valley, or may survive by hunting, foraging and raiding. Traps such as concealed pits and snares may have been created for protection or trapping animals for food.
- Goblins are raiding local settlements. Adventurers that try to fight them will face great numbers and the disadvantage of fighting enemies that know the terrain far better than they do.
Encounters & hazards
In the summertime, the tundra is teeming with life. Flowers peek through the melting snow. Lichens and moss cover the normally dried out ground. Melting water collects in ice-cold streams, fens and bogs. For a short period, the steppes are green with lush grass. As far as the eye can see, herds are grazing, such as wild steppe horses, pegasi, wooly rhinos, mammoths, bison, dire elk, reindeer, moose, caribou, etc. Insects are buzzing and crawling around. Hunting spiders pop out of their burrows to snatch unsuspecting snow rabbits. Giant landcrabs also lurk just under the surface. Massive flocks of migrating geese or swans pass overhead, or sometimes land to feed and rest. Vultures compete with flocks of crows or raven for carrion. Solitary birds, native to the steppe may include - amongst others - kingfishers, wren, buzzards, blackbirds, thrush, hawks and eagles. On top of the food chain are ferrets, weasels, stoat, packs of relentless hunting wolves, frost giants, ice dragons, polar bears, warm blooded multi-color-feathered raptors, yeti, wendigo, sabre tooth tigers..
Fens could easily house oozes or trolls, giant hibernating frogs or poisonous snakes, and shoals of predatory fish. Entire armies of frozen travelers stalk the tundra as zombies, skeletons or ghosts. Will-o-wisps lure adventurers into unforgiving swamps. Ice and wind elementals rule the plains. Storm giants roam the clouds. Evil fey whom no-one has ever heard of, are a completely new and terminal experience to be had. Underground predators such as purple worms and bulettes don't give a fuck about the weather and are a constant threat.
Even in summer, when food is plentiful and the weather is temperate, the tundra can be incredibly dangerous. Swarms of billions of mosquitoes can suck a herd of cattle dry in mere days. But even aside the beasts that come out of hibernation, there are other dangers to consider. A vast bubble of methane may be trapped just under the frozen ground, escaping from uncountable leaks in a large area, possibly replacing breathable oxygen, and certainly forming a violently flammable mixture with air.
In winter, ice covers most of the hard dirt, or snow is heaped up in meters-high dunes. Harsh blizzards are the constant killers of the tundra. Loose packed snow can and will slow progress to a near standstill. Due to the lack of visual landmarks, it's surprisingly easy to get lost on the tundra. A blizzard will reduce visibility to zero, while howling winds make it nearly impossible to hear each other. Explorers caught in a strong north wind would better know how to find or improvise shelter, lest they die an inglorious death by hypothermia. Where snow insulates frozen water, the ice may be too thin to carry a party of adventurers and their horses. Getting stuck under the ice is one acute problem. But even when successfully getting out of the icy water, getting a fire started quickly may be problematic, as solid ground to start a fire on, could be impossible to find.
Terrain features vary immensely. Where the thin top layer of dried-out grass or moss is gone, sand dunes are visible. Or the ground can be flat, strewn with boulders that sometimes reach as high as a house. Extensive fens may treacherously lurk under a thin layer of grass. Certain areas will probably have impassably steep canyons, with sinkholes and caves just under the surface for kilometers around. Gently sloping tableland is covered by vast stretches of pine forest or white birch woods. Meadows of high grass-like stalks reduce visibility and movement rate, and probably conceal predators. Cacti efficiently retain water, and carnivorous plants supplement their bare-soil diet with any available protein that happens to wander along.
Barbarian families of strong body and mind, build sturdy longhouses with walls of mud and timber and stone, covered with turf or thatched roofs. Or they dig into a hill like hobbits, exposing only a stone door to the outside. These large families typically occupy only one building, so settlements are small and wide spread. They have a very strong sense of honor and breaking a promise is a mortal sin. Their dead are buried under large piles of stones, or in cairns that are excavated.
The tundra is also shared with nomadic tribes, who have their own code of conduct and may be very warlike. Each tribe has a khan who leads. They respect tradition and their way of life immensely. Hospitality is valued greatly. Nomads can be trusted to repay a kindness sooner or later, but neither is a slight ever forgotten. Their camps consist of tents or yurts, made of sticks or bones that are covered with animal hides. These tents are designed to be dismantled and transported compactly. They break up camp to follow the herds, or they hole up in winter camps. Nomads are proficient riders and know how to use bow and arrow superhumanly well. They have little possessions. Nothing is wasted. Relations between nomadic tribes is strenuous at best, but a common cause may unite the nomads to be a force to behold. Nomads may put their dead on tall poles for birds to be eaten, or out in the plains for wolves, so their souls can become one with the steppe forever.
Life on the tundra is brutal and the weak will perish, due to the bitter cold, rugged terrain and difficulty of obtaining food.
- In an otherwise stone free landscape, in an easily overlooked shallow valley, you come across an enormous, overgrown heap of stones. Is this the grave of someone that was very well-respected, as lots of people must have brought a stone to pay their final respect? Some easy treasure may be up for grabs! Or did people from long ago wish for something to stay buried, so they piled as many stones as they could find in a 10-day radius? Still might be some treasure though! Hey what's that, every stone has a rune written on .. BOOM
- Lying on your back, chewing on a dry blade of grass, you notice a big bird flying high overhead. A very big bird... Couldn't be... Where would a dragon even have a lair in this godforsaken tundra. Wait, is our illusionist playing pranks again? Nope, he's still tied up and gagged in the back of the cart. Uh-oh.
- The long dark is coming. The steppe nomads prepare their most beautiful virgins ritualistically. This feeding ground is vast.
This is a perfect place for farming, with open space for planting crops or raising livestock, so expect scattered villages and towns. However, that doesn't make it safe.
- Bands of raiders (humans, goblins, orcs, something else?) are stealing the food that villagers work so hard to gather. The village needs someone to track down the culprit(s) and put an end to it.
- An unseen pack of predators stalks the grasslands, thriving on farm animals which are being bred for human consumption of their milk, wool and meat. Animal carcasses are dragged completely or partly underground, or horribly crushed with large slabs of flesh torn away in huge chunks.
- A herdswoman and her dogs haven't come back to the farm last night, and neither has the herd. Maybe she just sprained an ankle. In any case, someone should go looking for her.
Drier and less hospitable than a fertile grassland, where packs of predators hunt herds of prey. Settlements will likely consist of small villages that mainly keep cattle and try to grow crops.
They tower on the horizon for many miles around, a vast range of snow topped mountains. Dwarves, humans and other civilized creatures may make their homes within them, but so may other, more hostile creatures.
- A dangerous creature or creatures from the underdark are raiding above ground mining settlements within the mountains.
- Flying creatures from the peaks of the mountains are attacking towns and villages in the valleys below, and so heroes must climb to the peaks to destroy them.
Far from civilization, exotic jungles are places of giant trees as far as the eye can see, weird flowers and strange and often dangerous creatures. Exotic jungles are the natural habitat of savage tribes and wild natural beasts.
- A great treasure, important to a quest, is hidden in an ancient city in the heart of the jungle, guarded by a dangerous and almost unknown tribe and protected by traps that still work after 1000 years without maintenance.
- Settlements on the edge of an exotic jungle are under attack from monsters that dwell within the forest, perhaps angered by deforestation of their homes.
The lair of a dragon, usually containing a hoard of treasure. The level your players determine how old the dragon is and how many there are. Kobolds are common in a dragon's lair
- A dragon is terrorizing local townsfolk. Heroes are needed to slay it before it kills everyone!
- A dragon discovers an artifact/information and destroys a temple devoted to a deity of your choosing.
The Underdark is a vast collection of underground locations, spread out through the planet's crust, stretching from the surface world to roughly 22 kilometers deep (14 miles) where the magma mantle begins. The crust appears to be thinner underneath oceans, sometimes only being 5 kilometers (about 3 miles) thick.
Some of these sites are interconnected through passages, some are linked through magic portals. But some locations are completely isolated from anywhere else, and are only accessible by teleportation or burrowing.
Describing the Underdark is a daunting task, which is outside the scope of this overview of adventure locations and ideas. A great resource would be the Forgotten Realms campaign accessory Underdark, by Bruce Cordell, Gwendolyn Kestrel and Jeff Quick from WotC (this is not open content though), which has some very good descriptions and ideas which can be used in any campaign featuring underground exploring. Other great sources of inspiration are computer games Dwarf Fortress by the brothers Tarn and Zach Adams, Dungeon Keeper from Bullfrog Productions, and the legacy text adventure series Zork from Infocom.
With only very few exceptions, the underground is completely pitch black once you go deeper than a few meters, so adventurers would better be prepared with ample light sources. Torches will only last that long. For long lasting expeditions into the dark, bioluminescence could be used to create low-light conditions. Magical light sources also are highly valued when confronted with perpetual darkness.
- An aging dwarf has barricaded himself in a passage that leads deeper underground. Uncharacteristically, he has converted to a God of light, keeping this passage continuously lit by prayer. Wide-eyed, he proclaims to any passers-by that he has witnessed the Ur-Dark and survived. He keeps the darkness at bay and warns anyone who will listen not to descend any deeper past this point. Enticed by his stories of a lost community, adventurers ignore his pleas in search of loot. When they descend further, light sources start to wane, and it gets colder and colder...
- When traversing a large cave, explorers get shot at from beyond their visual range, by rapid, well aimed bow fire.
- While returning to base camp, your last torch slowly, yet deliberately, burns out prematurely. It is now pitch black. You are likely to be eaten by a grue.
Alternate means of "visualizing" the surroundings could consist of..
- Low light vision, also called starlight vision or cat vision, which still needs a very faint light source.
- Echolocation such as bats and grimlocks use.
- Vision into electromagnetic spectra other than visible light, such as thermal or ultra-violet vision, possibly even radio waves.
- Tactile perception. Some creatures can sense even the faintest of vibrations, for instance fish, spiders, burrowing creatures and earth elementals and kin. No-one is certain if oozes and jellies are able to sense their spacial dimensions, but sometimes they seem to move purposefully, possibly attracted by smell or acidity. Rodents and moles can feel their way around using their whiskers.
- Smell is often highly developed in blind creatures. The smell of blood could have predators tracking adventurers in an attrition hunt. Rotting meat attracts flies and carrion eaters.
- Magnetic perception. It is well documented that certain animals have a sense of magnetism which helps them navigate their surroundings. To what extent this enables them to visualize their surroundings is highly debatable. Expect the unexpected.
- Electric discharges, such as nervous activity, might be sensed by certain animals or monsters, like sharks for instance.
- Infravision. When not indicating low-light vision or thermal vision, infravision is sometimes a "magical" means of seeing in the dark. Creatures with infravision just "see" in the dark. Physics do not explain how infravision works exactly, as it is in the realm of fantasy or just beyond current understanding of the multiverse. This makes it very hard to blind a creature with infravision. In addition, it is entirely plausible that some creatures sense the flow of magic around them, even feeding of excess magical radiation, so adventurers might consider concealing the magic items they carry.
As mentioned above, many underground creatures have heightened auditory senses. Sound waves not only traverse the air in the underground hollows, but also travel through the rocks all around. Unnecessary noise like talking aloud, or walking too noisily, is likely to attract predators, resulting in the Underdark being very, very quiet. Adventurers might discovers this law of the Underdark the hard way.
For this reason, the drow have developed an intricate hand sign language. One advantage of this, is that a drow who is signaling his companions, is not wielding a weapon in the hand(s) he is signaling with.
Near to the surface, having a sufficient air supply is hardly ever a problem. When probing deeper into the depths, breathable air might be replaced with toxic fumes and gases. When navigating flooded underground passages, water breathing equipment or magic need to be brought along. Some underground plant life or chemical reactions could provide breathable oxygen.
- Guarded jealously by a clan of Duergar, is the knowledge how to produce oxygen for their underground city. It might be a portal to the plane of air, it might be a vast underground garden, it might even be their own cultivation of oxygen producing mold. Perhaps they have a huge electrical installation, electrolysing water into hydrogen and oxygen. Steal the evil dwarves' source of oxygen and exterminate them all in the process. Genocide is perfectly justified, because they are the evil enemy and we are the good guys. Right?
- An elf has devoted the remainder of his long life, to guard an underground burial site of a long forgotten evil. His self imposed prison holds a permanent source of sunlight, which provides his own micro-ecology with energy. An abundance of surface plant life provides all the oxygen his slow metabolism needs to endure the lonely ages.
- The corridor seems to briefly go down and back up a few meters, for no clear reason. The air doesn't smell any less stale down here, but the color of your torch's flame seems to be changi.. FFWWWOOOOOOMMM
The Underdark is a desert. Some locations have water in abundance, but one could wander through unmapped tunnels for months without finding any moisture at all. Most underground species need water too, so expect places where water accumulates or flows freely, to be infested with dangerous life forms, and/or actively guarded from intruders. Some water sources provide drinkable water, but many are contaminated with sulfur or other mineral solutions or hazardous parasites that make the water unsafe to drink.
Water seeps down through permeable layers (a.k.a. aquitards), until it reaches a layer of impervious rock or clay (a.k.a. aquiclude or aquifuge), through which the water cannot descend any further. Water accumulates here and flows much like rivers on top of this layer. These hollows can be saturated, being filled entirely with water, or they can be unsaturated, eroding expansive cave systems by underground rivers. Located below the impervious layer of rock which forms the bedrock of an aquifer, could be other layers of permeable / impervious rock, holding more aquifers, the deeper one goes. Some scholars claim there might even be entire oceans deep within the earth's crust.
Aquifers can be very useful or very dangerous. They often provide an unlimited supply of fresh drinkable water. Adventurers should be careful however, when excavating their own underground stronghold, especially when digging upwards. Should they hit upon an aquifer unexpectedly, the new struck well will flood all the levels below it, drowning everyone and making it inaccessible. Of course, collected water could also be used as a trap to drown unwanted intruders. Pre-installed pumps could empty flooded corridors, leaving the drowned corpses for easy and risk-free looting.
- An ordinary farm hamlet is being plagued by strange creatures. Cattle is being stolen and farms plundered. Witnesses have described the attackers to look very much like Kuo-Toa. But Kuo-Toa live in oceans or Underdark lakes, how did they get here, to the surface, in a peaceful meadowy countryside? Tracks could lead to the small lake where this Hamlet's mountain stream spring is located, or to a new sink hole closeby, revealing a new access point to the Underdark. Should authorities be warned of the impending dangers as soon as possible? Or perhaps adventurers could consolidate a position of some influence, by acting as an intermediary between the Underdark and the surface world.
The tunnels of the Underdark spread out three-dimensionally. When not being careful, one might get lost in the many branching and twisting tunnels that all look alike after any prolonged time underground. Larger caverns are seldom illuminated well enough by dim light sources, to easily notice exits which lie hidden in the twisting shadows that torches cast.
Only a fraction of tunnels, caves and caverns are easily walkable paths or stairs. Often, specialized climbing gear and know-how is required to climb safely up and down. In caves that hold water, moisture condenses everywhere, causing surfaces to be dangerously slippery. Cavern floors littered with stalagmites (or ceilings full of stalactites) could prove to be very hard to traverse. Snakes, snails, arthropods and flying creatures all have the advantage here.
Tunnels and caverns are sometimes flooded farther than one can hold his breath. Even proficient divers could suddenly get swept downstream for a potentially deadly wild water trip down a river, whirlpool, sinkhole or waterfall.
"These aren't just stone walls! Where do you think your fancy curved swords come from? Here's why geology is important, you butterfly smelling elf hippies!"
Rock or stone is a solid form of one or more minerals. As any dwarf worth his
metal mettle can tell you, stone comes in a large variety of sorts.
Stone holds the raw ore from which metal is smelted. To achieve high enough temperatures, other types of stone can be burned as fuel, like lignite, bituminous coal or coke. The resulting metal can then be smithed into various weapons and armors. To produce high quality steel, crude iron (a.k.a. pig iron) needs to be smelted with flux stone to absorb impurities into the slag. How to recognize which types of stone hold ore, which stones are flux stone, and knowing where to mine for them, are highly valued skills in any technological society!
In fact, the technological level of a society can be gauged by looking at the quality of the material of their soldiers' armor and weapons. Societies which do not have access to mining technology, might armor themselves in bones, keratin or chitinous or sea shells, wood, leather, ceramic, or even resin hardened layers of cloth. Metals are harder and sharper. Ranging from low to high quality are copper, bronze, iron, steel and mithril (a.k.a. adamantine).
A rock layer is also called a rock stratum (plural strata). Strata are made of the same types of rock, and are ordered in roughly horizontal sheets, which may span hundreds of thousand of square kilometers. Thickness of a rock layer can vary from a few millimeters to several kilometers. Based on the formation process, rock layers can be classified into 3 main types, sedimentary, igneous and metamorphic, but the changes from one form into another are gradual, making the classification of rock types a continuous spectrum.
The top layer at the surface is soil. Soil is for surface dwellers. It contains little of value.
Underneath the relatively thin layer of soil, lies sedimentary rock. This rock is composed of pressurized sediment, and is likely to contain fossilized plant material, petroleum and flammable gas pockets, which can be burnt as fuel. All flux stones (dolomite, chalk, limestone, calcite) except marble can also be found in sedimentary layers. Sedimentary layers often hold iron ores.
Igneous rock is cooled magma or lava. These strata very seldom have flux stone. Igneous rock contains gold, silver, platinum, lead and other metals. The most valuable gems can be found here, for instance diamonds. This rock stratum reaches all the way down to liquid molten rock, known as magma. Magma could be used as an alternate heat source for furnaces, in the absence of fuel.
By subjecting sedimentary or igneous rock (or even older metamorphic rock) to changes in pressure and/or temperature, these rock types are morphed into another form with profoundly different properties. Metamorphic rock is the only layer in which marble, which is a flux stone, can be found. Valuable gems can be mined in metamorphic strata.
- Two dozen or so dwarves are guarding a dark green metal gate to their kingdom. Their armors are made of colorful gleaming bismuth bronze-like metal. The one who's wearing the most oxidized armor, wordlessly looks you up and down, evaluating your weapons and armor. The dwarven silence takes on a snobbish flavor all of its own, as you are categorized as mostly harmless and allowed through.
- Having made contact with an Orog stronghold, you realize they have all the hematite they need to produce as much iron as they need. The only thing they need to upgrade their weaponry to steel, would be flux stone. As a "consultant" you could sell them chalk or limestone at exorbitant prices, or get paid even more by opposing governments to keep flux away from these Orogs. Alternatively, buy the iron ore from the Orogs, acquire flux stone yourself, melt and refine iron into steel, craft steel into weapons, sell weapons back to the Orogs (or to higher bidders who want to keep the Orogs subjugated).
- No matter how much exploratory mining we did, these strata do not contain any fuels. You will be paid extravagantly if you can bring us a captured and enslaved dragon or fire elemental, which we will then use to melt our raw ore.
The realm below the surface has its own ecology, housing species and biotopes of its own. Devoid of light, the Underdark ecology is not based on the energy which the sun provides. Instead, bacterial life, fungi, mosses, oozes and slimes provide the nutritional building blocks on which all other subterranean species depend. Note that some beings such as elementals, undead or golems do not really need any sustenance. Some burrowing species probably get their sustenance from the matter they "digest" before excreting it.
A wide variety of fungi, toadstools and mushrooms exists. Most are unhealthy or even poisonous to eat unprepared, in case of doubt "do not touch". Some fungi are ambulant, sometimes in search for carrion, sometimes actively hunting unwary prey. Some fungi live in symbiosis with other species, such as shriekers-violet fungi. Fungi may also be a hazard by releasing toxic or spores, incapacitating nearby victims, infecting breathing creatures to be the fungi's host, or infesting adventuring gear to the point of uselessness. Some species of fungi are reported to be sentient.
Arthropods such as insects, myriapods, crustaceans and arachnids, feed off fungal bio-mass, and off each other. Arthropod size varies for minuscule to huge. Many are poisonous to eat, or have a poisonous bite. Some species erode metals.
- Swarms of blood sucking insects make this passage impossible to traverse. Should we turn back and retrace our steps for many kilometers of tedious crawling? Or might these insects be cultivated as a buffer of protection by treasure hoarding Svirfneblin?
Snails are cold blooded and can sneak up on heat sensing dwellers of the Underdark. Some snails can squirt acid when threatened. Snails produce slime which can be very slick and sticky and hard to remove from weapons or clothes.
Oozes, puddings and slimes slither everywhere, even into very tight spaces and cracks, probing for sustenance. Many are carrion feeders, sometimes utilized by intelligent creatures as waste disposal. These may prove to be nearly indestructible adversaries which relentlessly follow their perceived prey.
Some worms are detrivores, some are parasites living of larger beings. Some species can grow to enormous sizes, digging tunnels of their own, such as purple worms.
Plankton may be found in large bodies of water, providing other animal life with sustenance. Coral, shellfish, anemones also populate water.
Small and medium creatures
Higher up in the food chain lives a myriad of life forms. A non-exhaustive list of examples are leeches, shrimp, crabs, eels, cave fish, jelly fish, frogs and toads, trolls, snails, lizards, turtles, piercers, ropers, stirge, cave fishers, bats, eye wings, birds, rothé, rats, spiders, hook horrors, snakes, driders, ankheg, mimics, minotaurs, quaggoth, umber hulks, troglodytes, xorn, giants...
While any sentient Underdark species might be tough prey to slay and eat, the Underdark fauna (and flora too) is certainly not above eating any stray stragglers who underestimate the environment.
Creatures at the top of the food chain have no natural predators. In the Underdark it is not clear which creatures, if any, have no natural predators. Mind flayers, dragons, beholders and aboleth might qualify as apex predators. If you're able to preserve their meat until you find the right vendor, you could make a fortune selling to the right chef. And don't forget that mages too are always looking for rare material components.
Doors, bottlenecks and fortifications
Passageways into lairs or underground communities are easily defensible. These avenues are very likely to be blocked or trapped. Dwarves, gnomes and orc-kin are renowned for their engineering skills. Passage into a stronghold could be barred by sluice-like chambers, where intruders can be easily observed, gased, drowned, fired upon, squashed, dropped into prison cells, and so on..
Oblivious spelunkers could easily pass by illusory walls, or magically conjured rock walls, without ever noticing anything out of the ordinary.
- The corridor you are about to enter is clearly artificially made. It is very straight and long (you can't see the end of it), and the right wall appears to be some sort of enormous monolithic panel. Just a little further in, you can see some large metal sheets which resemble flattened pieces of armor, surrounded by large patches of very fine white dust. The stop sign next to the entrance is probably for real.
- When you open the door to the next room, you are overwhelmed by the stench of rotting meat. A black cloud of flies engulfs you and obscures your sight. When you finally clear your mouth and nostrils and peer into the room, you see a walkway to a door on the other side, flanked on both sides by a long drop to a forest of glinting spikes. Everything, including the walkway, the ceiling and the walls leading down into darkness, are colored brown by many gallons of dried blood. The walkway is littered with skeletal limbs and body parts, lying in a wriggling white carpet of maggots.
- Your torches light a railroad track which lies a bit tilted, as if to support trains or wagons to take this turn without derailing. The curve of this tunnel is very slight though, and the tilt of those railroad tracks rather steep, suggesting extremely high speeds of passing railroad traffic. A faint rumbling can be felt coming from the floor, increasing in loudness rapidly.
- The obsidian floor in this enormous hall is perfectly smooth, as if solidified liquid stone. In several places there are imperfections though, where molten metals are embedded in the stone in a whirled pattern. Hahaha, stupid engineers made a mistake. *clunk* Where did the door go?