Pact of Undoing

Return target non-permanent spell to it's owner's
hand. It's controller untaps all lands tapped to
cast it. Until end of turn, that player cannot cast
that spell, or spells that share a name with it.
At the beginning of your next upkeep, pay {u}. If you don't, you lose the game.
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"Call this a warning. Try this feat again and my
mercy will grace you not."