The Abyssal Sovereign

Ecology
The Abyssal Sovereign is a miles-long, ancient Leviathan that has resided in the deepest, lightless trenches of the Broad Swells for millennia. It is a creature of pure muscle, armored scales, and crushing tentacles, rouse from its slumber by the dark rituals of the Obsidian Scale. It views the surface world as a mere source of food and its movements can trigger tsunamis that devastate entire coastlines.
Lair Actions
When fighting in the Abyssal Trench, the Sovereign can use the following lair actions:
- Pressure Spike: The water pressure in a 40-foot radius suddenly intensifies, dealing 6d6 bludgeoning damage and knocking creatures prone.
- Ink Cloud: The Sovereign releases a massive cloud of abyssal ink, heavily obscuring a 60-foot radius and dealing 4d6 psychic damage to any creature starting its turn inside.
- Tentacle Surge: Dozens of smaller tentacles erupt from the ocean floor, attempting to grapple and restrain all creatures in a 60-foot radius.
Combat Mechanics
A Kaiju-level threat, the Sovereign has multiple tentacle attacks, a crushing bite that can swallow Huge or smaller creatures, and an "Abyssal Roar" that causes psychic damage and permanent deafness. Its thick hide is resistant to all non-magical damage and it can use legendary actions to move or attack between turns.
Loot
The Sovereign's primary eye is a massive, glowing gem known as the "Eye of the Deep." It acts as a legendary scrying focus and grants the user the ability to communicate with all aquatic creatures.