Levith casts one of the following spells, requiring no material components and using Wisdom as the spellcasting ability (spell save DC 18):
Amphibious. Levith can breathe air and water. Kraken Connection. Levith has a connection with The Kraken which allows him to concentrate on two spells at once. Legendary Resistance (3/Day). If Levith fails a saving throw, it can choose to succeed instead.
Multiattack. Levith makes two tentacle attacks and one Sapphire of Power. Tentacle. Melee weapon Attack, +7 to hit, (one target) 5 (1d6+2) bludgeoning damage, and the creature must succeed on a DC 16 grapple check or they are grappled. Sapphire of Power. As an action, a creature grappled by Levith is pulled to the sapphire on his chest. They must make a Constitution saving throw DC 18 or take 3d6 necrotic damage. If a creature is killed by this ability Levith regains a spell slot. Voice of the Kraken (Recharges after a Short or Long Rest). The Kraken speaks through Levith with a thunderous voice audible within 300 feet. Creatures of Levith’s choice that can hear the kraken’s words (which are spoken in Abyssal, Infernal, or Primordial) must succeed on a DC 17 Wisdom saving throw or be frightened of Levith for 1 minute. They also take 3d6 psychic damage. A frightened target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
Levith can take 3 legendary actions, choosing from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. Levith regains spent legendary actions at the start of its turn. Tentacle. Levith makes a tentacle attack against one target. Water Teleportation. Levith or an ally he can see can touch a body of water at least 5 by 5 feet of water and teleport to another body of water at least 5 by 5 feet that is within 1 mile of each other. Kraken Presence (2 actions). The Kraken is always watching his servant and the overbearing power of his will forces all creatures within 60 feet of Levith must make a Wisdom Saving Throw DC 18. On a failure, the creature takes 4d6 psychic damage and suffers 1 point of madness. After 1 points of madness, they must roll on the "short-term madness" chart. After 3 points of madness, they must roll on the "long-term madness" chart. After 6 points of madness, they must roll on the "indefinite madness" chart.
When fighting inside its lair, Levith can invoke the ambient magic to take lair actions. On initiative count 20 (losing initiative ties), Levith takes a lair action to cause one of the following effects:
Levith lairs in an underwater castle that is based in one of the unknown domains of The Eternal Domain. The Kraken gifted him arcane crystals that he can use to shift his castle and the lake it inhabits to other planes of existence to hunt.
The region containing Levith's lair is warped by the creature’s presence, which creates one or more of the following effects: Underground surfaces within 1 mile of Levith's lair are slimy and wet and are difficult terrain. All water begins to move towards the lake that serves as Levith's lair. Eventually, it will all come together. If Levith dies, the first two effects fade over the course of 3d10 days.