Capitation

You cause confusion and befuddlement by creating an additional head on the shoulders of a targeted creature that immediately begins bickering and debating with the creature's existing head(s).

Target a creature that you can see within range that has at least one head and can speak at least one language and is not currently under the effect of this spell. The target must succeed on a Constitution saving throw or sprout an additional head next to its existing head(s). This head has the same Intelligence, Wisdom, and Charisma scores as the target, but its alignment is the opposite of the target's alignment and is friendly to you and your allies.

While this head exists, the target has disadvantage on ability checks, attack rolls, and saving throws made against you and your allies. If the targeted creature can take the multiattack or extra attack action, the conjured head gains control of one attack granted by this action. Any damage directed at the conjured head is taken by the targeted creature. 

If you maintain concentration on this spell for its full duration, the effect becomes permanent.