Sunken Rlyeh (5e Environment)

Sunken Rlyeh

Overview

A planar gate beneath the ocean’s surface leads to the Elemental Plane of Water (EPW) and the sunken city of Rlyeh. The location of the gate in the Prime Material (PM) plane is in the ocean at the furthest point from any surface landmass. This gate is normally hundreds of fathoms beneath the ocean surface there, at a depth of, say, 6000 feet. The shape and dimensions of the gate are impossible to describe, as it ebbs and flows like a tide; but it is enormous, at least a league across (about 3.5 miles).

Within this multi-dimensional gate, the PM plane and EPW coexist. Due to the ambient light emanating from the EPW, at night the gate appears to have a glow to it, such that it stands out to those who are directly above it and looking down into the ocean’s gloomy depths. From the EPW, the gate appears as a murky blackness against the infinite dim light of the elemental plane. Inside the gate, the lighting is roughly equal to that of the EPW. Any creature entering the gate from either direction, and then exiting, must determine which plane they are exiting to. There is simply a sense that there are two options; either the infinite ambient light of the EPW, or the cold darkness of the PM plane. When the gate volume is exited, the creature will then exist only in the desired plane, next to the gate.

Again many fathoms from the gate, in the EPW, the city of Rlyeh exists as a dark blot in the infinity of that plane, writhing and reaching for the gate as if a sentient being, intent upon grasping and owning the gate.

You Are Invited...

to contribute to the development of this wretched city. Unless your contributions are simply enhancements or improvements to previously documented material, please refrain from deleting anything; just add paragraphs in the appropriate sections and label them as "optional rules" or "alternative realities" or whatever. The original author (Dain) is looking for (begging for) good ideas and material to be added to make this a playable environment. Conflicts and contradictions are okay, because, well, it's Rlyeh. Truth on one side of the city may not be reliable on the other side, and the only constant there is change.

R'lyeh first appeared in H. P. Lovecraft's short story "The Call of Cthulhu". I've dropped the apostrophe in R'lyeh because of uncertainty where it might cause issues in a computer environment (like in filenames).

Description

Rlyeh is roughly spherical and many many leagues across. The geometry and architecture in Rlyeh are both alien and horrific to behold; nothing there is as it seems, causing dreadful effects to those gazing at the tremendous shifting visi-scape. Occasionally, when the stars are aligned to malignant effect, the whole city moves toward the gate, and some part of the city may actually pass to the PM plane and even breach the surface of the ocean there. This often appears as an unmarked isle in the middle of the ocean. When this happens, woe to those curious sailors or others of the PM plane who interact with Rlyeh and its denizens.

DM Facts: Rlyeh’s average diameter is about 36 miles. Its surface area is about 4000 square miles. This is roughly equivalent in area to that of present day Los Angeles. Rlyeh's entirety is tightly packed with hideous and alien towers, temples, great halls and compounds, and a variety of other buildings of unsavory or unknown purpose. Beneath the horrid surface is another world of tunnels, dungeons, and even more unspeakable horrors.

While there are no poles or rotation, to traverse the surface from a point to its polar opposite point on the other side of the sphere would be about 56 miles. There are many hills and elevation changes, but since the surface is densely packed with buildings and other structures, the curvature of the sphere is hardly noticeable.

When Rlyeh extends its reach into the PM plane, there is unrest in the Ethereal Plane parallel to the Material, and when extensions from Rlyeh actually breach the surface, across the whole world there are rare supernatural phenomena: dogs barking through the night, whispering winds, sudden storms, and the like. a hole basically appears in the Ethereal Plane's reach around the Material Realm, and spirits behave erratically at the border of this sudden gap.

Rlyeh is truly monstrous both in size and aspect. Due to the otherworldly nature of Rlyeh, its appearance is constantly changing and shifting. Looking at it with earthly eyes makes one feel tiny and insignificant. Those of weaker constitution may even feel slightly ill and uncomfortable. Towers and structures may seem to move or disappear, or change in appearance. Many of the structures are non-Euclidean in nature, and they are offensive to the unaccustomed eye.

Geometry Note: Math was not Lovecraft's strong point. Keep in mind that "non-Euclidean" is being used in a form adherent to the texts. In reality, this just means 3D structure. You and I both are in a non-Euclidean world as we speak. Therefore, it is highly suggested the DM come up with other inventive ways to describe this place as alien as possible.

Approaching the dark Rlyeh sphere, sparse dim pinpoints of light can be observed. Closer approach reveals more lights, and the brighter of these are seen to be greater concentrations of individual and mostly stationary light sources. These sources include a variety of types, including spells like continual flame, light, and environmental factors like luminescent corals and shells, as well as other less common magical and non-magical emanations.

Rlyeh's surface and buildings are mostly covered in a dark green slime, in many cases several feet thick. The exterior of the slime may still be slick, but the inner layers have likely solidified onto the surface. Many of the structures there are of massive size but seemingly simple in construction; huge blocks of stone are the primary building materials, with doors or passages large enough to accommodate creatures of gargantuan size. Other structures appear to have been built for creatures of varying size, mostly ranging from Medium to Huge.

The Ethereal Plane does not extend to Rlyeh’s location in the EPW.

Rlyeh was an apex city of the Great Old Ones millions of years ago, before the rise of men and elves. An unknown event caused the city to sink beneath the waves, and the elder gods lie in deathlike slumber in Rlyeh and possibly other locations on this planet, and possibly on other planets or planes. There they await a realignment of the stars, and the prescribed (or proscribed!) set of spells cast by their cult leaders, to awake them and free them to rule over the earth once again. The Great Old Ones, and in particular Cthulhu, communicate through dreams with those sensitive to their thoughts, and plot the rise of Rlyeh and the opening of their tombs.

Movement in Rlyeh

Rlyeh is an aquatic setting. As it is sunken, swimming is the common mode of transportation through the deluged city, and the creatures which inhabit it reflect this nature.

Directions are difficult to discern, and attempts to move toward an objective may leave outsiders farther from that object. Building interiors may seem impossibly large relative to the apparent outside dimensions, and interior openings may seem to extend into rooms that must be outside of the building.

Any outsiders attempting to move with or follow another traveler will become disoriented and unable to follow, unless tethered by rope or other physical constraints.

Vision and the Ill Effects of Vision Enhancement

Lighting

In and around Rlyeh, the ambient glow of the EPW is weak. It is a cold and dark city, and so vision is obscured. What can see here which does not belong may regret ever having lain eyes on the maddening effects of the place. Darkvision works normally. Normal vision is restricted to only a distance of 20 feet when in the open and not in a structure. Beyond that, lighting is about the equivalent of nightfall. Beyond the 20' limit, creatures that cannot see in the dark are considered blinded and automatically fail ability checks related to sight. They also take a -5 penalty to their Passive Perception and have disadvantage on their attack rolls. Inside unlit structures, darkvision or light sources are required to see.

Truesight

Because of the unfathomable and disturbing construct of the city, those who have truesight, or use true seeing or other sight enhancing effects will be stunned for one turn (immediately upon entering the city or initiating the enhanced vision sensing), and must make a Wisdom save against DC20 at the beginning of each of their subsequent turns or become/remain stunned. Out of combat, they must make this save every hour. They will remain so unless the sight enhancement effect is removed, or the character is blinded.

Blindsight

Blindsight is of no particular use in navigation, other than to avoid walking/swimming directly into an obstruction. But it remains effective in identifying locations of other beings within range.

Navigation

Parties attempting to move independently toward an objective will surely be scattered and separated. So long as a creature non-native to Rlyeh is within 30 feet of the city surface (including building tops), they have disadvantage on all checks related to navigation, including not getting lost or remembering where they have passed. One way of reorienting one’s self when lost, is to simply close one’s eyes and push off the surface, swimming away from the city. When far enough off the surface, a creature can gain a correct perspective, and swim in a direction accurately. Once closer to the surface again, the disturbing/offending visual effects resume.

Parties moving far enough above the surface level of the city are not subject to the maddening visual effects that afflict travelers within 30' of the surface. The dark blot of the gate might be used as a point of reckoning to orient oneself against the sinister darkness of Rlyeh itself. But travel above the surface of the city, in the open expanse where the ambient light of the plane exposes a party to risk of discovery, is extremely dangerous. Predators, slavers, zealots, and other threats will be drawn to visible groups traveling above Rlyeh's surface. These encounters may come from within the city, or from any direction in the watery expanse. DMs should check for encounters (1 chance in 6, cumulative, of an encounter for every 10 minutes spent above the cover of the city's "skyline") using either the Deep Water tables or the Rlyeh City tables, at the DM's pleasure.

Other Spells and Potions

Spells such as arcane eye might be useful if left in a stationary position, but attempts to move the eye within Rlyeh's zone of effect would result in the diviner losing track of the eye's direction and position. Similarly, the potion or spell clairvoyance could be used to scry a place which had been visited previously, but any attempt to spy upon a place that was only seen and not visited would most likely result in a miscast (use the random location table to determine where the casting lands).

Rlyeh "Society"

Rlyeh has no government or bureaucracy. Its denizens reside there at their own risk, or because they serve the purposes of more powerful creatures. Vast sections are unpopulated, or are haunted by fierce but unintelligent predators. Populated areas are kept more clear of the ever-present slime, either by intent or simply because of higher levels of traffic. The denizens of the city may coexist, but all are always ready to take advantage of the weakness of others, especially outsiders. The huge and powerful predators which lurk in the shadows near populated sections, have an innate sense that attacking the servants of Cthulhu or Dagon would be detrimental. Therefore, they do not hunt in those areas, and avoid what would sensibly be good hunting grounds. They will intuitively recognize outsiders, and will have no hesitation in attacking them. Common predators are creatures like the shoggoth, who roam the dark streets.

A premise of this environment is that Cthulhu, and possibly other Great Old Ones, remain in their deathlike slumber at Rlyeh for now. Alternatives realities may negate that premise, as there are plenty of ominous prophecies foretelling the day when the Great Old Ones may rise again, and Rlyeh shall be expelled from the bowels to be exposed to the world.

Structures of Rlyeh

Before the sinking of Rlyeh, it was a flat, coin-shaped island floating on the ocean. When it sank and was thrust to the EPW, it eventually “adjusted” to its new environs, and mutated to its current spherical shape. Most of the structures kept their shape, but as if responding to the needs of its survivors (and many new inhabitants), Rlyeh has reshaped itself to accommodate the will of its “dead” masters. Buildings in general in Rlyeh are very symbolic and often religious in origin. They are of shapes that would not be soundly found in usual architecture and use geometrics that one would never think of in their wildest dreams. Some may find looking at these discomforting due to an uncanny feel. Despite the wear and tear of the ages, the sturdiness of the structures speaks to the time-tested powers of the Great Old Ones. The overall look and feel of the city are unnatural and alien, with archways and balconies along the street that look out into the dark city.

Notably, there are also usually scrawls of writing on the thresholds and arcs along the building walls. This language was originally an alien one, with a script similar to that of the illithid's written language of Qualith. Being with origins from the Far Plane, it utilizes strange curved symbols like runes. Sometimes they can form vast murals on walls depicting history. The elder things were believed to have used this language as well in their fine and bizarre architecture above waters. This was later imitated by their slave shoggoths who built underwater structures.

There is a slight gravitational pull toward the Rlyeh sphere, due to its massive size in the otherwise non-gravitational Elemental Plane of Water. Debris outside the sphere that are within a distance at least half of the city's radius will occasionally float towards the city limits. However, this does not impede one's ability to swim along or away from the surface of the city.

Navigating Rlyeh

Some of the structures in Rlyeh can be identified by pictographs in the Tongue of the Great Old Ones. But many of these identifiers are hidden by the thick layer of slime coating. These signs may be read by creatures with the comprehend languages spell, or by those conversant in Tongue of the Great Old Ones, or by even guides familiar with the city.

Guides may be hired from the local population, but their trustworthiness may be of questionable value. These are people who have dwelt in Ryleh since before its sinking into the sea, and this, coupled with the mental sovereignty of their sleeping gods, has changed them. Guides are able to navigate the non-Euclidean and alien nature of the city, and can lead parties by rope or chain (or possibly by other means). They will faithfully and correctly lead pilgrims, couriers, VIP visitors, and the like, but if it is recognized that parties are explorers, treasure hunters, or adventurers, they are likely to be led to the lair of some horrid creature, and dumped there. The typical cost of a guide is 2gp per person per hour, to be paid in advance.

Because of the difficulty of navigating in Rlyeh, a "Locations" table is provided to randomly determine the next building, structure, or location that the party encounters. They may think they are heading to some observed object, but getting there is problematic, and where they end up is purely random.

Locations Table

DM determine if location is populated by denizens from Rlyeh encounter table.

DM determine if area is slime-covered or cleared, unless otherwise noted.

DM deterimine if there are light sources; if not, creatures may be hiding inside, ready to pounce…

The size noted is indicative of the original intended occupancy. "Any" means that any size of creature might have used, occupied, or otherwise benefited from this feature.

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d100	location feature	description
1	House of Cthulhu	120' tall door into the side of a domed hill or mountain. Huge stele with pictograph inscription, covered in slime, identifies this as Chulhu's crypt. Don't try to go in! It is watched by many sets of eyes, be they allies or enemies. Any attempt at intrusion will result in a swift intervention.
2	tower, gargantuan	a cyclopean tower with open windows and doors, large enough to accommodate a gargantuan creature.
3	tower, huge	a cyclopean tower with open windows and doors, large enough to accommodate huge creatures.
4-5	tower, medium/large	a cyclopean tower with open windows and doors, large enough to accommodate medium/large creatures.
6	temple, gargantuan	a temple, large enough to accommodate a gargantuan creature.
7	temple, huge	a temple, large enough to accommodate huge creatures.
8-9	temple, medium/large	a temple, large enough to accommodate medium/large creatures.
10	teleport/plane shift sigil, gargantuan/huge	a sigil inscribed on the floor of a huge open plaza, cleared of slime.
11	teleport/plane shift sigil, medium/large	a sigil inscribed on the floor of a large open plaza, cleared of slime.
12	stadium, large	an open coliseum of sorts, for large creatures.
13	amphitheater, huge	a descending amphitheater with stadium seating, for huge creatures.
14	amphitheater, medium	a descending amphitheater with stadium seating, for medium-sized creatures.
15	arena, huge	a closed roof arena, for huge creatures.
16	arena, medium/large	a closed roof arena, with seating for medium and large creatures.
17	prison/holding cells, huge	a prison or holding area with cells, sized for huge creatures. If occupied, the prisoner(s) may be selected from among any of the encounter tables, but will be of the appropriate size, and will be intelligent.
18	prison/holding cells, medium/large	a prison or holding area with cells, sized for medium and large creatures. If occupied, the prisoner(s) may be selected from among any of the encounter tables, but will be of the appropriate size, and will be intelligent.
19	torture chamber, medium/large	a torture chamber in an enclosed structure, sized for medium and large creatures. If occupied, the prisoner(s) may be selected from among any of the encounter tables, but will be of the appropriate size, and will be intelligent.
20	apothecary, medium/large	Run by a local, roll on Rlyeh encounter table until appropriate proprietor is identified.
21-22	laboratory, large	Run by a local, roll on Rlyeh encounter table until appropriate lead (mad) scientist is identified.
23	dome, gargantuan	enclosed dome, sized for one or more gargantuan creatures.
24	dome, huge	enclosed dome, sized for one or more huge creatures.
25-26	dome, medium/large	enclosed dome, sized for medium or large creatures.
27-29	air bubble/dome/room, huge	An air-breathing, surface-dwelling creature may be found here; is it a prisoner, an ally, a ???
30-31	air bubble/dome/room, medium/large	An air-breathing, surface-dwelling creature may be found here; is it a prisoner, an ally, a ???
32	great hall, gargantuan	enclosed great hall with many ante-rooms, sized for many gargantuan creatures.
33	great hall, huge	enclosed great hall with many ante-rooms, sized for many huge creatures.
34-35	great hall, medium/large	enclosed great hall with many ante-rooms, sized for many medium or large creatures.
36	courtyard, gargantuan/huge	formerly a meeting area or parade grounds, but after millions of years, ???
37	courtyard, medium/large	formerly a meeting area or parade grounds, but after millions of years, ???
38-40	market/meeting area, any	This area is densely populated by a variety of diverse and intelligent life forms. Anything and everything is for sale here. Bickering and bartering are constant. But if an attack is made, the populace are all armed and ready to defend the common "good".
41	sphere, gargantuan	a cyclopean sphere with open windows and doors, large enough to accommodate a gargantuan creature.
42	sphere, huge	a cyclopean sphere with open windows and doors, large enough to accommodate huge creatures.
43-44	sphere, medium/large	a cyclopean sphere with open windows and doors, large enough to accommodate medium/large creatures.
45-46	monument, open, any	an open monument garden, with slime-covered obelisks and other markers, describing the arrival of the Great Old Ones, battles and slaughters, etc.
47	monument, enclosed, gargantuan/huge	an enclosed monument to the Great Old Ones, with markers and wall reliefs, depicting their power and glory; sized for huge or gargantuan creatures.
48-50	monument, enclosed, medium/large	an enclosed monument to the Great Old Ones, with markers and wall reliefs, depicting their power and glory; sized for medium or large creatures.
55	garden, gargantuan	formerly a garden, but after millions of years, ???
56	garden, medium/large	formerly a garden, but after millions of years, ???
57	great machinery (purpose = ???), any	an unimaginably large enclosed structure housing operating machinery that would be alien to any earth dwellers; there are gears, pistons, pulleys, etc, along with undescribable gizmos, all of tremendous size.
58	house, gargantuan	a stone block house for some creature of gargantuan size.
59-60	house, huge	a stone block house for some creature of huge size.
61-62	house, large	a stone block house for some creature of large size.
63-64	house, medium	a stone block house for some creature of medium size.
65	chapel, huge	a chapel for worship of one or more of the Great Old Ones, sized for huge creatures.
66	chapel, large	a chapel for worship of one or more of the Great Old Ones, sized for large creatures.
67-68	chapel, medium	a chapel for worship of one or more of the Great Old Ones, sized for medium creatures.
69	bazaar, huge/large	This area is densely populated by a variety of diverse life forms. Anything and everything is for sale here. Even more so than the market, services and goods can be had here. But if an attack is made, the populace are all armed and ready to defend the common "good".
70-71	bazaar, medium/large	This area is densely populated by a variety of diverse life forms. Anything and everything is for sale here. Even more so than the market, services and goods can be had here. But if an attack is made, the populace are all armed and ready to defend the common "good".
72	slave market, medium/large	This is a bustling area with numerous simultaneous slave auctions conducted. There are also sales of beasts of burden, goods for restraint and punishment, etc. Guards of all appropriate races are abundant.
73	inn, huge	Even a strange and forbidding location like Rlyeh has travelers and guests. This inn caters to huge creatures. It is mostly clear of the slime that permeates much of the city.
74	inn, large	Even a strange and forbidding location like Rlyeh has travelers and guests. This inn caters to large creatures. It is mostly clear of the slime that permeates much of the city.
75	inn, medium	Even a strange and forbidding location like Rlyeh has travelers and guests. This inn caters to medium-sized creatures. It is mostly clear of the slime that permeates much of the city.
76	tavern, medium/large	A meal or a deal can be had in this tavern catering to medium and large creatures. It is mostly clear of the slime that permeates much of the city.
77	tavern, large/huge	A meal or a deal can be had in this tavern catering to large and huge creatures. It is mostly clear of the slime that permeates much of the city.
78	tavern, huge	A meal or a deal can be had in this tavern catering to huge creatures. It is mostly clear of the slime that permeates much of the city.
79	DM special	Ad lib a special purpose building, event, or encounter that will entertain and enrich the party (or put an end to their unwelcome meddling in the affairs of the Great Old Ones). If possible, draw upon prior adventures, encounters, or experiences that will have meaning to the party.
80	charnel house, any	This gigantic building is a dumping ground for corpses, husks, and remains. And the proprietor is frequently able to resell items. It does a brisk business in Rlyeh...
81	barracks, medium	Soldiers of any of the various factions may bunk here in this barrack for medium-sized creatures.
82	barracks, large	Soldiers of any of the various factions may bunk here in this barrack for large creatures.
83	barracks, huge	Soldiers of any of the various factions may bunk here in this barrack for huge creatures.
84	compound, gargantuan	This is a complete set of buildings for a gargantuan creature or creatures. It is typically a walled space with a house, one or more watch towers, out-buildings for manufacture or repair of armor, weapons, jewelry, or whatever. There may be barracks and/or a holding cell area as well.
85	compound, huge	This is a complete set of buildings for a huge creature or creatures. It is typically a walled space with a house, one or more watch towers, out-buildings for manufacture or repair of armor, weapons, jewelry, or whatever. There may be barracks and/or a holding cell area as well.
86	compound, medium/large	This is a complete set of buildings for a medium-sized creature or creatures. It is typically a walled space with a house, one or more watch towers, out-buildings for manufacture or repair of armor, weapons, jewelry, or whatever. There may be barracks and/or a holding cell area as well.
87	time/space gate, any	These gates are extremely dangerous; they can accommodate any size of creature. Pictograph instructions and warnings in the Tongue of the Great Old Ones should provide at least a clue that this space should not be traversed without a great deal of preparation.
88	incubation chamber, large	a special closed, locked, guarded, and warded building for the purpose of egg incubation; select race or roll to determine one randomly. This one is for eggs of a large species.
89	incubation chamber, medium	a special closed, locked, guarded, and warded building for the purpose of egg incubation; select race or roll to determine one randomly. This one is for eggs of a medium species.
90	tunnel, gargantuan	a sub-ground-level tunnel large enough for gargantuan creatures; it has many branches and intersection, and direction and distance are impossible to determine. The non-Euclidean nature of the entire city is especially confusing here, as branches seem to twist and turn in impossible loops. Without a guide, one could become lost forever here.
91	tunnel, huge	a sub-ground-level tunnel large enough for huge creatures; it has many branches and intersection, and direction and distance are impossible to determine. The non-Euclidean nature of the entire city is especially confusing here, as branches seem to twist and turn in impossible loops. Without a guide, one could become lost forever here.
92	tunnel, medium/large	a sub-ground-level tunnel large enough for medium or large creatures; it has many branches and intersection, and direction and distance are impossible to determine. The non-Euclidean nature of the entire city is especially confusing here, as branches seem to twist and turn in impossible loops. Without a guide, one could become lost forever here.
93	alley, large	an alley with impossible twists and turns, large enough for large creatures. Slime-filled, with forbidding towers looming overhead. Shadows flit and eerie sounds or vibrations fill one with a sense of foreboding.
94	alley, medium	an alley with impossible twists and turns, only large enough for medium creatures. Slime-filled, with forbidding towers looming overhead. Shadows flit and eerie sounds or vibrations fill one with a sense of foreboding.
95	pain shop, large/huge	a little shop of horrors for large or huge creatures wanting "treatment". Always open for business; DM should determine if there are currenly customers, and who/what they are.
96	pain shop, medium/large	a little shop of horrors for medium or large creatures wanting "treatment". Always open for business; DM should determine if there are currenly customers, and who/what they are.
97	holding area, caged (slaves, beasts, etc), medium, large, huge	Similar to a slave market, but for beasts of non/low intelligence, and some very unfortunate slaves. DM determine the current prisoners, guards, vendors, and customers.
98	monster hole, size dependent upon inhabitant(s), if any	Carved or dug out of hillsides, buildings, or pits, monster holes are the lairs of monsters from the encounter tables. The lairs of great non-intelligent beasts are always watched by intelligent scavangers, who wait until the beast is away, and then seach the lair for treasure items that have been consumed and subsequently deposited there.
99-00	thoroughfare, any	Main thoroughfares are streets, paths, bridges, etc, large enough to accommodate gargantuan creatures. In spite of their size, they are difficult to navigate; streets that seems to be open and straight for great distances, may suddenly turn or dead end.

Encounter Tables

Three tables are provided for encounters on the ocean surface, in deep water, and in Rlyeh. Each table has five columns containing encounters for parties of average level groupings ranging from 5 to 21+.

Sunken Rlyeh Ocean Surface Encounter Tables: Those adventurers native to the Prime Material Plane who are foolish enough to seek Sunken Rlyeh must find the location of the gate. An encounter table for the ocean surface is provided. These encounters would occur on the open seas near the surface point above the gate.

Sunken Rlyeh Deep Water Tables: An encounter table is provided for deep water encounters, which would occur in the Prime Material Plane near the gate, or within the gate itself, or in the Elemental Plane of Water near the gate.

Sunken Rlyeh City Encounter Tables: An encounter table is provided for the city of Rlyeh. In conjuction with the "Locations" table, a complete adventure in Rlyeh may be quickly constructed by populating structures or locations with creatures randomly selected or placed by the DM. This encounter table may be used either way.

Intelligent creatures without Darkvision or other means of sight enhancement will typically have access to a dim magical or non-magical light source, although if in an area of sufficient light to move about, that source may be covered or shuttered, to avoid attracting unwanted attention.

Breathing, Swimming, and Combat Underwater

Be mindful that many methods and devices for breathing water do not confer any special underwater movement, and the many methods and devices for underwater movement (swim capability) do not provide the ability to breathe underwater. Parties will need these capabilities for long periods of time in order to properly explore the sunken city of Rlyeh.

Also, creatures without a swim speed, spell, or device to provide swim capability are at a disadvantage in combat with many weapons. The sheer oddity of the city and pressure of the waters make their movements sluggish, giving them disadvantage on their weapon attack rolls.

Total immersion in the city provides resistance to fire damage, and things do not ignite in the city as an effect of spells or mundane effects.

Environment and Spell Effects

The temperature and pressure in this area of the Elemental Plane of Water are manageable. Despite the high underwater pressure in the Prime Material Plane at the depth where the gate lies, water only slowly diffuses through the gate. This defiance of physics is attributed to the unknown cosmic forces. Since the gate is porous and allows exchange of liquids, the salinity of EPW in the vicinity of the gate and Rlyeh is roughly equal to that of the PMP's earthly oceans. Thus, players normally cannot fulfill their daily water requirements with such salty water.

It is assumed that whatever spells or abilities allowing characters to breathe water and swim proficiently also allow those characters to tolerate the pressure and water temperature at the depth of the gate in the PMP.

Water related spells (shape water, control water, e.g.) on the EPW may, at the DM's discretion, have their effects enhanced or magnified. These effects could/should be consistent with those discovered in any prior excursions to the EPW. If this is a party's first visit, the DM should consider in advance how to modify the effects of any water-related spells or items available to the party. Spells with mind-altering effects like charm person, as well as others on the Great Old One warlock spell list, are also subject to undue interference, such as commands which come from thin air or voices that jam attempts to communicate via spells.

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