Hydra
Huge Monstrosity, unaligned
3,900 XP
Special Abilities
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 25 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 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.
Actions
Multiattack
The hydra makes as many bite attacks as it has heads.
Bite
Melee Weapon Attack: +8 to hit, reach 10 ft., one target. Hit: 10 (1d10 + 5) piercing damage.
Quick Reference
Running This Encounter
The Hydra is a devastating melee combatant that excels in prolonged fights due to its multiple heads and regeneration. Use its 5-foot reach to threaten multiple party members simultaneously and position it in terrain that limits ranged escape routes. The creature's regeneration (10 HP per round if it has at least 1 HP) means parties must deal significant damage quickly or use fire/acid damage. Remember that when the Hydra takes 25 or more damage in a single turn, one of its heads dies permanently, and this is the only way to permanently reduce its threat.
Combat Tactics
The Hydra attacks with all available heads each round, making multiple bite attacks against different targets to spread damage and reduce healing efficiency. It uses its multiattack relentlessly, prioritizing targets that seem weakest or most isolated from the group. If forced to retreat, the Hydra regenerates and returns to combat rather than fleeing permanently.
Environment & Setting
Hydras thrive in swamps, marshes, or shallow lakes where their multiple heads give them vision advantage and they can use water for tactical positioning. Ideally place the encounter in terrain with difficult movement, such as murky water or overgrown vegetation, to prevent easy kiting.