Control Rune

You can carve a Rune into a war of clay, and once that rune is hardened, attach it to the undead with a small string or tie. Infuse the rune with necrotic energy (touch it) and then the rune will sink into the undead, letting them be under your control forever until they die.

6 spell slot or higher used to cast the spell lets you fill the undead to either be able to cast a cantrip once a day, or explode into 6d8 necrotic damage when killed, healing you and ally’s who get hit by the necrotic explosion for all the damage it deals. If your health is full you get temporary hp for all the leftover health.