Entrap the Weaver

You attempt to take possession of a creature in the process of casting a spell. If this spell normally targets only one creature, the target of this spell must succeed on a Wisdom saving throw, or change the target of their spell to affect a new target of your choice, that you can see other than yourself,  and within range of the redirected spell's range.

The secondary target treats the spell as having originated from the original caster, using their Spellcasting ability modifier, save DC and spell attack bonus.

Creatures that can't be charmed are immune to this effect.

Each time the target tries to cast a spell that targets only one creature, they make a new Wisdom saving throw against this spell, on a fail, you may use your reaction to redirect the spell. If the saving throw succeeds, this effect ends.