Skithiryx, the Infection

Flying, Infect, Trample
{b}{b}{g}{t}: Target creature gains infect until end
of turn
{b}{g}: put a -1/-1 counter on target creature
Whenever one or more poison counters are
put on a player, you may put that many -1/-1 counters on target creature they control.
Whenever a creature with a -1/-1 counter on it
dies, that creature is exiled instead.