Force Shapechange

With this spell, the caster can force any shapechanger or magic-wielder using any form of a shapechanging spell to instantly revert to his true form (or his most common form). To use the spell, the caster points at creatures he knows or believes to be shapechangers. If the creatures are indeed shapechangers, they must make a successful saving throw or immediately revert to their true form and suffer 3-30 (3d10) hit points of damage from the wracking pain caused by the forced change. The change takes a full round, during which time a victim can take no other actions.
If the saving throw was successful. the victim does not change form, but still suffers half damage (2d10/2).
The material components for this spell are released when the verbal component is uttered.

[Complete Wizard's Handbook]

School: Necromancy
Level: 5
Rarity: Very Rare

Range: 10 yards/ level
Components: V, S, M
Duration: Instantaneous
Casting Time: 1
Area of Effect: One creature/level
Saving Throw: 1/2

Material Components:
a hair from the hide of any lycanthrope and a live butterfly