Hydras are multi-headed classical guardians of entrances to the underworld, much like the Chimera. They are about as big as rhino, four legged and flightless, with multiple snake or dragon heads. Roll 1d8+4 to determine the number of heads. Each head is worth one HD (in terms of to-hit), 8hp and one bite dealing 1d10. For every 8hp lost, a head is lost. For every head lost two new heads will grow back the next round with 8hp each, increasing the hydra’s ferocity. A hydra can have up to twelve heads unless the wounds are cauterized using ice or fire, e.g. a flaming or freezing weapon is used, or somebody else hits the hydra with a burning torch whenever a head is chopped off. The torch will cauterize the wound without dealing additional damage.
A hydra can breathe fire 3×/day. Like dragon fire, it deals as much damage as the hydra has hit-points, save vs. dragon breath for half damage. It’s blood is poisonous: cutting off one of its heads with a melee weapon will expose the attacker to its cursed poison, save vs. poison or die. Dipping arrows or other weapons in the hydra’s blood will poison them: the next time they deal damage, the victim must save vs. poison or die. The hydra itself is immune to fire and poison.
HD 1 per head (8hp per head) AC 5 1d10 per head MV 12 ML 9 XP depends on the number of original heads (5: 650; 6: 1070; 7: 1490; 8: 2060; 9: 3100; 10: 3100; 11: 3600; 12: 3600); regrowing heads (up to 12); fire breath; poisonous blood; save as fighter of the same level as number of heads