Hydra

Huge Monstrosity, Unaligned

AC 15     Initiative +4 (14)
HP 184 (16d12 + 80)
Speed 40 ft., Swim 40 ft.

Ability Scores
STR 20 (+5) Save +5    DEX 12 (+1) Save +1    CON 20 (+5) Save +5
INT 2 (−4) Save −4    WIS 10 (+0) Save +0    CHA 7 (−2) Save −2

Skills Perception +6
Immunities Blinded, Charmed, Deafened, Frightened, Stunned, Unconscious
Senses Darkvision 60 ft.; Passive Perception 16
Languages None
CR 8 (XP 3,900; PB +3)

Traits

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

Multiple Heads. The hydra has five heads. Whenever the hydra takes 25 damage or more on a single turn, one of its heads dies. The hydra dies if all its heads are dead. At the end of each of its turns, if it has at least one living head, it grows two heads for each head that died since its last turn—unless it has taken Fire damage since its last turn. The hydra regains 20 Hit Points when it grows new heads.

Reactive Heads. For each head the hydra has beyond one, it gets an extra Reaction that can be used only for Opportunity Attacks.

Actions

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

Bite. Melee Attack Roll: +8, reach 10 ft. Hit: 10 (1d10 + 5) Piercing damage.