Hydra

From Kingdom Hearts - Wiki on Neoseeker

the hydra is a three headed serpent,its most powerful possession is its regeneration, Hercules first, cut of the lernian hydras head,and then it regenerated (it grew two more heads) regeneration is the most powerful thing in the world, basically, regeneration is like living forever (you cut one head of you grow two more you cut another head of you grow two more)thats why the hydra can not die it doesn't even have a heart its like a ghost!