Entice the Unholy

Entice the Unholy costs {1} more to cast for each nonblack creature.
Nonblack creatures get +4/+0 and gain
menace until end of turn. Destroy those
creatures at the beginning of the next end
step.
"Seek salvation in the arms of death..."
"...and know that in doing so you will serve more purpose than you ever could have hoped to while living."