This spell allowed the caster to increase the number of undead creatures they could control at a single time. The amount of undead the caster could control was determined by their skill level. The lasted a day, after which the caster lost control as if they had voluntarily given it up.
In addition to verbal and somatic components, the spell required a divine focus. The caster focused on the darkness in their soul, willing it to increase and grant greater power over the undead.