Call Upon the Dead

This spell only works on undead creatures. When cast on an undead within range, the soul of the person whose body the undead is now using is called upon to help. If the soul dislikes its former mortal body being used in necromantic ways, it comes to aid you and the spell comes into effect. If the soul has no issue with its former body being an undead, the spell fails and the spell slot is lost. The soul appears in a translucent and softly glowing shape adjacent to the creature and envelops it, beginning a struggle between the soul and the undead creature. The soul has no HP and can't be avoided, attacked or killed, but magic-dispelling effects will send the soul back to the afterlife.

When this spell comes into effect, the creature begins to struggle with the called soul over possession of the body. The creature must make a wisdom saving throw on the start of each of its turns, and if it fails it is paralyzed for the rest of the turn. On a successful save, the spell remains in effect, but the target is not paralyzed that turn. If the target completes three successful saves then the spell ends without any further effects, but if the target fails  three of its saving throws then it is both paralyzed that turn and  takes 8d6 radiant damage. The saving throws don't have to be consecutive, only cumulative; just like death saving throws. When three failed or successful saving throws are completed, the spell ends. Once the spell ends, the soul that was called upon returns to the afterlife regardless of the state of the target.

Casting this spell with a higher level spell slot allows you to target one additional creature for every two spell slots above 3rd you use.