Plague Dragon

Flying, haste.
Mutate 3 (If this creature would untap during your untap step, you may instead put three +1/+1 counters on it.)
{b}, Remove a +1/+1 counter from Plague Dragon: Target creature defending player controls gets
-X/-X until end of turn, where X is the number
of +1/+1 counters on Plague Dragon. Activate this ability only if Plague Dragon is
attacking.