Blackveil Vaal-Hazak

Flying, Fear, Infect
At the beginning of your upkeep, proliferate.
At the beginning of your endstep, if Blackveil
Vaal-Hazak attacked this turn, you may remove
X -1/-1 counters from targets dealing X damage
to each target that lost a counter this way.
{4}{b}{b}: target gains decayed