Doomsday Excruciator slots into Mono-Black decks as a finisher. The Demon costs six Black mana to cast, but is a 6\/6 with Flying. Doomsday Excruciator also has an ETB trigger in that opponents must exile all but the bottom six cards on their library, essentially putting all players on a six-turn clock. And as a bonus, you get to draw an extra card at the start of your upkeep, while your opponents are on a six-turn clock (not including damage).<\/p>
The cost of six Black pips could restrict the use of Doomsday Excruciator, but the Demon can get cheated out, whether through reanimation or even Manifest Dread in conjunction with Hauntwoods Shrieker.<\/p>