Those who expect betrayal at every turn are seldom disappointed.

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.

Mystery Booster 2

At that moment Gandalf lifted his staff, and crying aloud he smote the bridge before him.

Tales of Middle-earth Commander

Time Spiral Remastered

The List

Amonkhet Remastered

Although originally printed with a characteristic-defining ability that defined its color, this card now has a color indicator. This color indicator can't be affected by text-changing effects (such as the one created by Crystal Spray), although color-changing effects can still overwrite it.

If Pact of Negation is countered or otherwise doesn't resolve (perhaps because its target became illegal), the delayed triggered ability that threatens you with a game loss won't trigger at the beginning of your next upkeep.

If Pact of Negation resolves with a legal target but fails to counter that spell (most likely because that spell can't be countered), the delayed triggered ability will still trigger at the beginning of your next upkeep and you will have to pay. Or else.