The spell works much like polymorph, except rather than changing your body, you send forth your spirit, which materializes in the desired form next to your body, leaving your body in a state of suspended animation. Your spirit suffers any damage that your body does, and vice versa while the spell lasts and the death of either your body or your materialized spirit is fatal to you.
This spell is compatible with ethereal projection and greater ethereal projection, and allows your ethereal spirit to materialize in whatever form you wish. Shamans often use polymorphic projection to send their spirits out in the form of various animals or beasts while their bodies appear to sleep. They also use it to fight shapeshifting duels against one another.