Cthulhu

Traits

Amphibious

Cthulhu can breathe air and water.

Darklord Restoration

If Cthulhu dies, it revives with all its Hit Points in 1d10 weeks inside the Vault of Cthulhu.

Impossible Geometry

Ground, air, and water in a 10-foot Emanation originating from Cthulhu is Difficult Terrain. A creature that starts its turn in the Emanation takes 7 (2d6) Bludgeoning damage.

Legendary Resistance (4/Day, or 5/Day in Domain)

If Cthulhu fails a saving throw, it can choose to succeed instead.

Magic Resistance

Cthulhu has Advantage on saving throws against spells and other magical effects.

Actions

Multiattack

Cthulhu makes three Eldritch Claw attacks and uses Spellcasting to cast Befuddlement if available or Mind Spike (level 4 version). It can replace one Eldritch Claw attack with a use of Tentacle.

Eldritch Claw

Melee Attack: +17, reach 10 ft. Hit: 18 (2d8 + 9) Slashing damage plus 9 (2d8) Acid damage. If the target is a Large or smaller creature, it has the Grappled condition (escape DC 19) from one of two limbs.

Tentacle

Constitution Saving Throw: DC 25, one creature Grappled by Cthulhu. Failure: 21 (6d6) Acid damage plus 13 (3d8) Psychic damage. Success: Half damage. Success or Failure: The target's Hit Point maximum decreases by an amount equal to the Psychic damage taken, and Cthulhu regains Hit Points equal to that amount.

Bonus actions

Warp

Cthulhu teleports to an unoccupied space it can see within 120 feet, taking creatures it is grappling with it. Then each creature within 10 feet of the space it left is subjected to the following effect. Strength Saving Throw: DC 25. Failure: 7 (2d6) Bludgeoning damage plus 7 (2d6) Thunder damage, and if the target is a Large or smaller creature, it has the Prone condition. Success: Half damage only.

Legendary action uses: 3. The creature can use one option at the end of another creature’s turn and regains spent uses at the start of its turn.

Legendary actions

Clamp

Cthulhu makes an Eldritch Claw attack.

Fold Space

Charisma Saving Throw: DC 25, each creature and object that isn't being worn or carried in a 10-foot-radius Sphere centered on a point Cthulhu can see within 60 feet. Failure: 36 (8d8) Force damage, and the target is teleported to an unoccupied space within 60 feet of Cthulhu that is horizontal to it. Success: Half damage only. Success or Failure: Cthulhu can't take this action again until the start of its next turn.

Spellcasting

Cthulhu casts one of the following spells, requiring no spell components and using Intelligence as the spellcasting ability (spell save DC 25):

At will: Mind Spike (level 4 version)

3/day each: Dream, Geas (can target creatures through dreams)

1/day each: Befuddlement, Plane Shift (self only)

Regional effects

Innsmouth is altered by Cthulhu's presence, creating the following effects:

• Choking Depths: A creature can hold its breath for only 30 seconds while in the domain.
• Closing the Borders: While in its domain, Cthulhu can close or open the borders of Innsmouth at will. While the borders are closed, those who enter the Mists surrounding Innsmouth become lost at sea amid inky fog for 3d4 days before arriving once more at Innsmouth.
• Something in the Air: Creatures other than Cthulhu and its allies have Disadvantage on saving throws to avoid or end the Frightened condition.

If Cthulhu dies, these effects end immediately.