Lair of the Dark Beast of Waves (5e Environment)
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Greater Beast's Lair
In a large area in the Sea of Calnome, the Greater Beast of Waves makes its lair. An area where it is always raining, and the waves are so treacherous it would topple any ship that enters the lair, with an endless rainstorm whose clouds block out any sunlight from entering the area, and it will be dark out during the day and through the night.
Journey to the Lair
It is impossible for the party to swim to the beast and they would have to get a ship to fight it. If they become close to the leader of Farwater city they could be given a military ship, or they could hire a brave or foolish captain to bring them to the lair. The party will need deal with the waves somehow, or the ship will be sunk in a heartbeat, I recommend contacting a master abjuration wizard to magically strengthen the boat and reduce the power of strong waves and currents, likely one from the Arcadian Mage Guild or the Arcadian Rebels. Then they could travel to the center of the lair and fight the Beast
In this fight the party will be fighting in a boat, if the boat sinks, the party will die. So, the boats is the thing the beast will be breaking, and the boat's health is what the party will need to keep track of in this fight. Also fun fact. Salt Water conducts electricity. The sea of Calnome is a salt water sea. So... if a player misses the beast and hits the water with a lightning spell any creature within 150 feet of where the water was hit will still take the damage.
Greater Dark Beast of Waves
Damage Vulnerabilities Lightning, Radiance
Bite. Melee Weapon Attack: +15 to hit, reach 5 ft., one target. Hit: 63 (5d12 + 30) damtype damage. The beast attempts to bite of a chunk of the boat.
Tsunami. (Recharge 4-6). The powers of the beast causes a large 100 foot wave to hit the boat. The boat must make a DC 28 Constitution saving throw. It takes 112 (3d20 + 80) force damage on a failed save, or one-fourth as much damage on a successful one.
A giant leviathan like creature, almost 2 miles long, and 25 feet wide. It has a dozen webbed appendages it uses to propel itself through the water at rapid speeds each with a hooked claw at the end of each of them. With one giant mouth taking up all of the beasts head, that can open up to 60 feet to swallow something. The water around the beast will turn into a current propelling the creature faster in the direction that it is going. Its body made of water which seems takes the form of a scaly fish like creature, and though it is liquid it is almost feels hard like a solid.