Slaughter Pact

Destroy target nonblack creature.
At the beginning of your next upkeep, pay {2}{B}. If you don't, you lose the game.

Stifle

Counter target activated or triggered ability. (Mana abilities can't be targeted.)

Overkill

Target creature gets -0/-9999 until end of turn.

Cunning Wish

You may reveal an instant card you own from outside the game and put it into your hand. Exile Cunning Wish.

Ravenous Trap

If an opponent had three or more cards put into their graveyard from anywhere this turn, you may pay {0} rather than pay this spell's mana cost.
Exile target player's graveyard.

Pact of Negation

Counter target spell.
At the beginning of your next upkeep, pay {3}{U}{U}. If you don't, you lose the game.