Curse Walker

Double strike, lifelink, deathtouch
Whenever Curse Walker deals damage to a
planeswalker or player, each opponent gets a
curse counter and you put a +1/+1 counter on
each wraith, specter, shade, knight, and
snow creature you control. (Spells you cast cost 1
more life to cast for each curse counter you have.
Whenever you gain any life, remove all curse
countes you have.)