Whenever Charnelhoard Wurm deals damage to an opponent, you may return target card from your graveyard to your hand. Jund's dragons hoard only sangrite crystals. Its wurms aren't so picky.
Illus. Lars Grant-West
2/1/2009: If Charnelhoard Wurm is dealt lethal damage at the same time it deals damage to an opponent, Charnelhoard Worm will be in your graveyard by the time you put its ability on the stack. In that case, you can target it with its own ability.