Legendary Resistance(3/day)  If the Hydra fails a save, it can choose to succeed instead.

Hold Breath. The hydra can hold its breath for 1 hour.

Multiple Heads. The hydra has five 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 hydra takes 60 or more damage in a single turn, one of its heads dies. If all its heads die, the hydra 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 or radiant damage since its last turn. The hydra regains 10 hit points for each head regrown in this way.

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

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

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

Bite. Melee Weapon Attack: +8 to hit, reach 15 ft., one target. Hit: 10 (1d10 + 5) piercing damage.

Eldritch Mind Recharge (5-6). The Hydra chooses 3 enemies within 30 feet of it that it can see. Those enemies make Intelligence Saving Throws DC 14. On a fail- the target becomes frightened until the end of its next turn, as Yog-Sothoth's whispers pierce its mind. If the player fails the save by 5 or more, they are Stunned instead. They repeat the save at the end of their turns.

Acid Spray Recharge (4-6). The Hydra spews acid in a 30 foot cone. Enemies caught in the spray must make a DC 18 Dexterity Saving Throw. On a fail, they take 10d4 Acid damage, and another 5d4 acid damage at the end of their next turn. On a success, they take half as much damage, and no damage at the end of their turn

Chomp (1 Action) The Sotthian Hydra makes a Bite attack. If it hits, it makes a grapple contest against the target, and cannot use that head to attack. At the end of the grappled creature’s turn, it takes 5 piercing damage.

Acid Spray (2 Actions) The Sotthian Hydra uses its Acid Spray.

Eldritch Mind (3 Actions.) The Sotthian Hydra uses Eldritch Mind