Aemoldok, the Deathgrip Crab

Amphibious. Aemoldok can breathe air and water.

Keel Breaker. Aemoldok deals double damage to objects and structures

Legendary Resistance (2/Day). If Aemoldok fails a saving throw, it can choose to succeed instead.

Rigid Shell. Aemoldok cannot squeeze through smaller spaces.

Spider Climb. Aemoldok can walk on ceilings and on vertical surfaces without needing to make an athletics check or use additional movement.

Multiattack. Aemoldok makes two attacks in any combination of Claw and Grasping Tentacles, and uses Shell Slam or Swallow.

Claw. Melee Attack Roll: +13, reach 10 ft. Hit: 24 (4d8 + 8) bludgeoning damage. If the target is a Large or smaller creature, it has the Grappled condition (escape DC 18) from one of two claws.

Grasping Tentacles. Melee Attack Roll: +13, reach 30 ft. Hit: 18 (2d10 + 8) Slashing damage. If the target is a Large or smaller creature, it has the Grappled condition (escape DC 16).

Shell Slam. Constitution Saving Throw: DC 18, Any creature within 10 ft of Aemoldok. Failure: 24 (4d8 + 8) thunder damage and is knocked prone. Success: Half damage.

Swallow. Dexterity Saving Throw: DC 16, one creature Grappled by Aemoldok (it can have up to two creatures swallowed at a time). Failure: 30 (4d10 + 10) Piercing damage. If the target is Large or smaller, it is swallowed and no longer Grappled. A swallowed creature has the Restrained condition, has Total Cover against attacks and other effects outside of Aemoldok, and takes 21 (7d6) Acid damage at the start of each of its turns. At the end of its turn, it can repeat the saving throw to end this condition. Success: Half damage and the creature is not swallowed.

Legendary Action Uses: 3. Immediately after another creature’s turn, Aemoldok can expend a use to take one of the following actions. Aemoldok regains all expended uses at the start of each of its turns.

Fling. Aemoldok throws a Large or smaller creature Grappled by it to a space it can see within 30 feet of itself that isn’t in the air. Dexterity Saving Throw: DC 18, the creature thrown and each creature in the destination space. Failure: 18 (6d6) Bludgeoning damage, and the target has the Prone condition. Success: Half damage only.

Move. Aemoldok moves up to its speed.

Voice of the Grave. If Aemoldok is grappling a corpse, it can speak through it and invoke fear. Wisdom Saving Throw: DC 19, each creature in a 15 ft radius of the corpse. Failure: 16 (2d10 + 6) psychic damage and the target becomes Frightened for the next minute. They may repeat the saving throw at the end of each turn, ending the effect on a success. Success: Half damage.