Corvis, Leader of the Plague

First Strike
Black creatures you controll have "Whenever
this creature deals combat damage to a player,
that player discards a card"
Whenever a black creature you controll leaves
the battlefield, return it onto the battlefield
with a -1/-1 counter on it. Next you may play
another nonlegendary creature from your hand
without playing its mana cost. it enters the battlefield with a -1/-1 counter on it