Summon the Damned

Summon the Damned resolves in {x} upkeeps after it is played. When Summon the Damned is resolved, exile it.
For the duration it's in play, Summon the Damned allows its controller to spend black mana as though it was any color, reduces the cost of all black creatures by {2}, and gives all black creatures Flash.
When Summon the Damned is resolved, each creature put into play using the effects of Summon the Damned must be sacrificed.