Nightmare, King Darkness

Trample, first strike, menace
Affinity for rogues
Whenever a creature enters the battlefield, if an opponent cast if, you may pay {b}. If you do, it's controller loses 1 life. If you cast it, other creatures you control gain deathtouch until end of turn.
{2}{b}{b}{b}: Deal X damage to target creature,
where X is your devotion to black.