If it was cast upon a living person, the spell transformed them into a more powerful undead being, such as a ghast, wight, or, in the case of extremely powerful evil clerics, a vampire. This transformation took the spell's entire 10-minute casting time to take effect. During this time, the spell's effects could be dispelled or otherwise negated by disrupting the caster.
The undead minion created by this spell was fully under the command of the casting cleric. If they died, the undead creature was destroyed or granted free will.
In addition to verbal and somatic components, create undead minion required a number of material components: the holy symbol of the casting cleric, soil taken from a cemetery, and a fingernail taken from the type of undead the caster wished to create.