"Probably because it eats anything and everything." Adam froze the two heads and hung them from a tether behind him, then spoke to the devil. "Energy can't come from nowhere. Whether true undead exist, I can't say for certain, but the snow worm's regeneration is probably because it stores everything it eats inside its body as energy."
Adam stamped one foot on the ground, clearing away the floating ice and the snow. Beside a fractured sheet of ice he saw a great many energy stones. He picked one up and said, "So it looks like the energy stones really are its droppings, and it absorbed most of the rest of the energy."
Then he sank his sharp claws into the snow worm's head. "Let's see whether this thing has a soul." If he could sign a contract with a snow worm, it would help his plans enormously.