Opposite Day

9th-level transmutation

Casting Time: 1 action

Range: 1 mile

Components: V, S, M (a diamond-dust-laced hourglass worth at least 25,000 gold pieces, which is consumed)

Duration: 24 hours, or until dispelled

Opposite Day is one of the mightiest spells a mortal creature can cast. You radically invert the fundamental laws of reality in a 1-mile radius centered on yourself for the duration.

When you cast this spell, any attack roll, ability check, or saving throw has its result inverted. If any of these types of rolls would have previously been successful, they now become failures, and if it would have been a failure, it is now a success. Additionally, any roll that would have advantage instead has disadvantage, and any roll that would have had disadvantage now has advantage.

The stress of casting this spell leaves you devastated by reality-backlash. For the next 24 hours, you suffer 3 levels of exhaustion and any spell you cast has a 33 percent chance of failing automatically. Additionally, every time you cast this spell, there is a cumulative 33 percent chance that you can never cast Opposite Day ever again.