Teregud of the Corrupted

Infect
When a creature you control infects another creature or player, add an additional -1/-1 counter. At the beginning of your attack phase you gain X life where X is the number of creatures with a -1/-1 counter on them. If a creature would die by infect exile that creature instead and gain X life where X is that creatures converted mana cost. If a creature you control gets a -1/-1 counter, instead put a +1/+1 counter on it.