Is there a spell or ability anywhere that changes casting costs to black?
Closest thing I can think of {Initiates of the Ebon Hand}
Probably doesn't help but
{Urborg, Tomb of Yawgmoth}
You could use {Gilded Lotus}.
Or would that be to slow?
There's a card in innistrad that lowers casting cost...umm...
{heartless summoning}