Cataclysmic Failure

8th-level divination
Casting time: 1 reaction, which you take when a creature you can see within 60 feet of you succeeds on a saving throw or uses its Legendary Resistance trait
Range: 60 feet
Target: Special
Components: V, S (ebony scissors)
Duration: Instantaneous
Classes: Artificer, Cleric, Druid, Wizard
Subclasses:

You conspire with the forces of destiny to create the worst case scenario for the triggering creature. You change the creature’s successful saving throw to a failure. If the effect that required the saving throw would deal damage to the creature, the creature takes double damage from the effect this turn.