Astrid's Alter Outcome

Attuning yourself to existence, you gain a limited control over reality for a short amount of time. When you cast this spell, roll a d20. When you make a ability check, attack roll, or saving throw for the next hour, you may instead decide to use this saved roll. You may only replace your roll once, then this spell ends. You may do so after the initial roll, but not before knowing the outcome. 

This spell is under the school of Astrumancy

At Higher Levels. When you cast this spell using a spell slot of 4th level or higher, the duration of this spell extends by one hour per spell level.