That\\\'s my horse

Wither (This deals damage to creatures in the form of -1/-1 counters.) Whenever a creature an opponent controls with a -1/-1 counter on it dies, you may return that card to the battlefield under your control.

Flying When this creature enters, each player loses 3 life.

You can't get poison counters. Creatures you control can't have -1/-1 counters put on them. Creatures your opponents control lose infect.