Similar to the priest spell invisibility to undead, the affected person or creature could move and operate with impunity near undead, as long as they took no hostile action, including attempts to turn them. If an attack was made by a cloaked creature, only the target undead noticed—the spell was not broken for other undead nearby. This spell worked flawlessly every time on lower-level undead, but less often against the more powerful. No vampire was ever known to be fooled by this spell.
The spell required verbal, somatic, and material components, including a pinch of powedered silver and a piece of bone.