Your studies in transmogrification have increased your control over shapechanging spells.
Prerequisite: You must be at least a 5th-level Wizard to select this discovery.
Benefit: When you cast a spell of the polymorph subschool on yourself, you may expend 1 minute of the spell’s duration as a standard action
to assume another form allowed by the spell. You can do this as often
as you like, subject to the duration of the spell. This is a supernatural ability.