Aetherdrain

Necro {1}(When you cast this spell, you may remove
a creature card with {1} in its casting cost from your graveyard. If you do, this spell costs {1} less to cast.)
When target nonartifact creature spell resolves, it enters play as a colorless artifact creature with X
-1/-1 counters on it, where X is equal to the
number of colored mana symbols in its mana
cost. At the beginning of your next main phase,
add X black mana.