Amphibious. The abyssal human can breathe air and water.

Freedom of Movement. The abyssal human ignores difficult terrain, and magical effects can't reduce its speed or cause it to be restrained. It can spend 5 feet of movement to escape from nonmagical restraints or being grappled.

Multiattack. The abyssal human makes three tentacle attacks, each of which it can replace with one use of Fling.

Tentacle. Melee Weapon Attack: +17 to hit, reach 30 ft., one target. Hit: 20 (3d6 + 10) bludgeoning damage, and the target is grappled (escape DC 18). Until this grapple ends, the target is restrained. The abyssal human has many tentacles, each of which can grapple one target.

Fling. One Large or smaller object held or creature grappled by the abyssal human is thrown up to 60 feet in a random direction and knocked prone. If a thrown target strikes a solid surface, the target takes 3 (1d6) bludgeoning damage for every 10 feet it was thrown. If the target is thrown at another creature, that creature must succeed on a DC 18 Dexterity saving throw or take the same damage and be knocked prone.

The abyssal human 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. The abyssal human regains spent legendary actions at the start of its turn.

Tentacle Attack or Fling. The abyssal human makes one tentacle attack or uses its Fling.

Ink Cloud (Costs 3 Actions). While underwater, the abyssal human expels an ink cloud in a 60-foot radius. The cloud spreads around corners, and that area is heavily obscured to creatures other than the abyssal human. Each creature other than the abyssal human that ends its turn there must succeed on a DC 23 Constitution saving throw, taking 16 (3d10) poison damage on a failed save, or half as much damage on a successful one. A strong current disperses the cloud, which otherwise disappears at the end of the abyssal human's next turn.