Just play it when you have creature superiority, and you win.
Suddenly, neither player can play creatures, with very few exceptions.
And I hear black can sometimes kill creatures...
...except for the fact that it costs 8 mana, making it unplayable in any deck. D'OH!
Yeah, I see it in some type of Monoblack control deck. The casting cost is probably too prohibitive. But it would combo well with a Plague Wind played just before...
Okay, that's going way too far...
Rector maybe? Although a deck that uses this and is better than existing Rector decks...