Disruption

This spell targets a single creature that you can see within range, capable of casting any sort of spell, including psionic disciplines, and any abilities that consume spell slots, such as the paladin’s Divine Smite. The target must succeed at a saving throw that is based on your spellcasting ability. The Weave becomes chaotic about the target and on a failed save, the target’s ability to cast spells disrupted. Any spell it was concentrating on is automatically ended. 

Each time the target attempts to cast a new spell, it must succeed at the save again. Failure means it wastes its action trying and failing to cast the spell (and the spell slot/psi points are consumed regardless). Success means its spell/psionic discipline casts as normal, and ends the disruption spell.

On a mystic’s failed save, their focus is ended and cannot be reactivated for the duration.