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.

Summoner's Pact

Search your library for a green creature card, reveal it, put it into your hand, then shuffle.
At the beginning of your next upkeep, pay {2}{G}{G}. If you don't, you lose the game.

Slaughter Pact

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

Mana Short

Tap all lands target player controls and that player loses all unspent mana.

Hive Mind

Whenever a player casts an instant or sorcery spell, each other player copies that spell. Each of those players may choose new targets for their copy.