The Lernaean Hydra

Gargantuan monstrosity, unaligned

Armor Class 18 (natural armor)
Hit Points 525 (30d20 + 210)
Speed 30 ft., swim 40 ft.

STR	DEX	CON	INT	WIS	CHA
27 (+8)	7 (-2)	25 (+7)	4 (-3)	17 (+3)	13 (+1)

Saving Throws Str +15, Con +14, Wis +10
Skills Intimidation +8, Perception +17
Damage Immunities acid, poison
Senses darkvision 120 ft., passive Perception 27
Languages –
Challenge 23 (50,000 XP)

Special Traits

• Amphibious. The Lernaean Hydra can breathe air and water.
• Burning Blood. When the hydra takes piercing or slashing damage, each creature within 5 feet of the hydra takes 10 (3d6) acid damage.
• 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, or knocked unconscious. Whenever the hydra takes 40 or more damage in a single turn, one of its heads dies. If all its heads die, the hydra dies. At the end of each turn, it grows two heads for each that died since its last turn. The hydra does not regrow heads that have been destroyed by fire damage. The hydra regains 10 hit points for each head regrown in this way.
• Reactive Heads. For each head the hydra has above one, it gets an extra reaction that can be used only for opportunity attacks.

Actions

• Breath Weapon (Recharge 5-6). The Lernaean Hydra exhales burning poison in a 60 ft cone. Each creature in the affected area must make a DC 22 Dexterity saving throw, taking 40 (9d8) acid damage and 40 (9d8) poison damage on a failed save, or half as much damage on a successful one.
• Multiattack. The hydra makes as many Bite attacks as it has heads and one Tail Swipe attack.
• Bite. Melee Weapon Attack: +15 to hit, reach 20 ft., one target. Hit: 19 (2d10 + 8) piercing damage.
• Tail Swipe. Melee Weapon Attack: +15 to hit, reach 25 ft., one target. Hit: 17 (2d8 + 8) bludgeoning damage. In addition, the target must succeed on a DC 23 Strength saving throw or be knocked prone.

Legendary Actions

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

• Detect. The hydra makes a Wisdom (Perception) check.
• Move. The hydra moves up to half its movement speed.
• Attack. The hydra makes a Bite attack or Tail Swipe attack.

About

The Lernaean Hydra, or – more commonly – the hydra, is an aquatic monster with many heads that lives in the lake Lerna situated above the entrance of the underworld. It’s breath is said to be so poisonous that just breathing it is enough to be burned from the inside. The hydra’s main, and most well-known, strength is the ability to regrow two heads each time one is cut down; making it a fierce opponent for even the most legendary warriors.