Nightmarish Serpent

Deathtouch, Curse {3}{u}{u} (If you cast this card for its curse cost, it's an Aura spell with enchant player. It becomes a creature again if it's not attached to a player.)

Whenever enchanted player is dealt damage, you may create X 1/1 snake creature tokens and lose X life, where X is the damage dealt.
Those aren't butterflies wriggling in your stomach...