Hold Breath. The void abomination can hold its breath for 1 hour.

Multiple Heads. The void abomination has fifty heads. While it has more than one head, the hydra has advantage on saving throws against being blinded, charmed, deafened, frightened, stunned, and knocked unconscious.

Whenever the void abomination takes 10 or more damage in a single turn, three of its heads dies. If all its heads die, the void abomination dies.

At the end of its turn, it grows two heads for each of its heads that died since its last turn, unless it has taken fire damage since its last turn. The void abomination regains 10 hit points for each head regrown in this way.

Reactive Heads. For each head the void abomination has beyond one, it gets an extra reaction that can be used only for opportunity attacks.

Wakeful. While the void abomination sleeps, at least one of its heads is awake.

Multiattack. The hydra makes as many bite attacks as it has heads.

Void Tentacle. Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 10 (1d10 + 5) piercing damage.

The void abomination can take 2 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 void abomination regains spent legendary actions at the start of its turn.

Detect. The void abomination makes a Wisdom (Perception) check.

Horn Attack. The void abomination makes a horn attack.