Alter Time Flow

7th-level transmutation (temporal)

Casting Time: 1 action
Range: Self (30-foot radius)
Components: V, S, M (an hourglass)
Duration: Concentration, up to 1 minute

You control the currents of time, affecting all creatures within 30 feet of yourself. You can choose to deliver either a haste or slow effect (as the spell) to each creature in the area. An unwilling creature makes a Constitution saving throw, avoiding the effect on a success. Each unwilling creature must make a new saving throw if it remains in the affected area at the end of its turn. Any affected creature returns to normal if it exits the area, but if a creature reenters the area while the spell is still active, it is subject to the effect of the spell (and receives another saving throw, if unwilling).