This effect will remove all harmful effects from the spirit, leaving protectives. “Harmful effects” includes everything in the effects groups Alteration, Binding, Command, Curse, and Necromancy as well as the Stun Limb effect.
It will not remove effects in the Greater Command group. It will not cure any damage previously wrought by any effect, nor will it fix Instant effects which have already run their course (such as Doom). Similarly, Purify will not otherwise remove external effects (such as Wall of Force or Prison) even if the caster interprets them as “harmful.”
This spell will affect an undead as a Drain affects the living. It is also a very good in-game cure for an in-game hangover.
“I call upon Earth to Purify you.”