Grela, Bane of Serra

Flying, Deathtouch, Nemesis (When this creature enters the battlefied, choose target creature an opponent controls as its nemesis. While both creatures are on the field they cannot block creatures other than their nemesis.)
When Grela, Bane of Serra enters the battlefield create two X/X black fallen angel creature tokens with flying.
{t}: Place a doom counter on target creature.
{t}: Destroy target creature with a doom
counter on it.