Impostor

First Strike, Deathtouch
If this creature would die, exile it instead.
Impostor's power is equal to your devotion to
black.
{b}{b}{b}: Destroy target creature or planeswalker.
When you do, opponents may tap two nonblack creatures they control. If they do, exile Impostor.
For every card you control named Impostor on
the battlefield or in exile, black sorcery and enchantment spells you cast cost {1} less to cast.