Haster, Nightmare in Black

Deathtouch

When Haster, Nightmare in Black enters the battlefield, add X +1/+1 counters for every creature in exile and graveyards

Every time a creature your opponents control is sent to exile or the graveyard, gain X +1/+1 counters equal to that creatures converted mana cost. If Haster, Nightmare in Black has twelve +1/+1 counters on it at any time, you may expend them all and flip Haster, Nightmare in Black.