Braxases Spell Slip

When a creature in range that you can see uses an action to cast a spell, you can use your reaction to pull a random alternate reality version of that creature into being. The creature must make a Wisdom saving throw or be Charmed by you until the beginning of its next turn, creatures immune to Charm automatically succeed their saving throw.
While Charmed by you the creatures action is replaced by the action of an alternate version of itself. Instead of casting the intended spell it instead cast a random spell, with a casting time of one action, from their prepared spell list, centered on themselves. If, as part of the spell, other creatures, locations or objects are required to be selected, theses are selected at random. Material costs for the spell is ignored. If the creature was already concentrating on another spell, the new spell takes priority. The creature must attempt to hold concentration until the Charm effect ends.  If the creature is unable to cast any other spells it completes its original spell, but centered on itself.