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With this spell, you force any shapechanger to revert into its true form.
When you cast the spell, you specify the targets you know or believe to be shapechangers.
Any shapechangers targeted by the spell must attempt Will saving throws.
If they fail their saves, they revert to their true form amid wracking pain, which causes them 3d10 points of damage.
If the saving throw is successful, they retain their current form, but still suffer extreme pain, taking half damage.
The shapechanger is locked into its true form for 1 round per caster level, but the spell deals the 3d10 points of damage only when the change first occurs.
For purposes of this spell, a shapechanger is any creature with the shapechanger type or a supernatural or extraordinary ability that allows it to assume an alternate form.
A wu jen who knows polymorph self is not a shapechanger (since a spell is not a supernatural or extraordinary ability), but a spirit centipede is (since it has the exceptional ability to assume alternate forms, though its type is outsider).
This spell has no effect on creatures under the effect of alter self, polymorph self, or other spell effects.