Heroslayer Hydra
Huge natural beast (reptile)
Level 20 Solo Brute XP 14000

Initiative +14        Senses Perception +19; all-around vision
HP 776; Bloodied 388
AC 32; Fortitude 34, Reflex 30, Will 30
Saving Throws +5
Speed 6
Action Points 2

(⚔) Bite (standard, at-will)

Reach 3; +23 vs AC; 1d10+8 damage.

⚔ Hydra Fury (standard, at-will)

The heroslayer hydra makes five bite attacks, plus an additional attack for each head it has grown (see regenerating heads). A target hit by more than one bite attack in a round takes 10 extra damage

⚔ Rampage (standard, recharges when a critical hit is scored against the heroslayer hydra)

The hydra makes one bite attack against each enemy within reach. On a hit, the target takes ongoing 10 damage (save ends)

Heroslayer

While a heroslayer hydra is marked, it gains a +2 bonus to attack rolls and a +5 bonus to damage rolls against the creature that marked it.

Many-Headed

Each time a heroslayer hydra would become dazed or stunned, it instead loses one attack while using hydra fury during its next turn. The hydra can be dazed or stunned multiple times.

Regenerating Heads

When a heroslayer hydra first reaches 582, 388, and 194 hit points, a head is destroyed. At the start of the hydra's next turn after a head is destroyed, two heads grow in the lost head's place, and the hydra gains an additional bite attack with hydra fury.

Threatening Reach

A heroslayer hydra can make opportunity attacks against all enemies within its reach (3 squares).

Alignment Chaotic evil        Languages -
Str 23 (+16)      Dex 19 (+14)      Wis 18 (+14)
Con 26 (+18)      Int 2 (+6)      Cha 9 (+9)

Published in Monster Manual 2, page(s) 150, Dungeon Magazine 170, page(s) 20.