Hydras

A hydra is a reptilian, amphibious beast with the curious ability to regrow its severed heads. A hydra commonly has five heads, but hydras with up to a dozen have been reported. Hydras possess perhaps the greatest regenerative abilities in existence; their heads regrow near instantaneously, and wounds to the body, tail or limbs--however grievous--regenerate immediately.

Hunter's Notes

Hydras are vicious creatures of primal instinct and hunger. In battle, a hydra will move to where its heads can be near to as many foes as possible and each head typically chooses its own target. The regenerative abilities of a hydra leave its body and tail effectively immune to harm; a hydra can be slain only by severing its heads and cauterizing the wounds with fire. Hydras usually hunt and dwell alone except when mating.

Variants

On rare occasion, a hydra will mutate and acquire a deadly breath weapon of acidic slime. This caustic spray is ejected from each head independently, and therefore grows stronger with a greater number of heads.

Gatherer's Notes

Heartblood. The blood left in a hydra's heart at its time of death is useful for powerful regenerative magic, such as Rings or Potions of Regeneration or Periapts of Wound Closure are common reasons for the foolhardy act of hydra-hunting.
Extra skulls. A hunter with an eye for gold may consider that the teeth, eyes, skulls and brains are of moderate use to alchemists and arcanists; a greater number of heads equates to greater profit.