Changeling

Changeling is a spell that can switch minds and bodies. It is activated by reading a incantation after which a sudden strange light engulfs and switches the bodies. Also the spell has to be deactivated within 30 minutes or the minds will never go in their original bodies. If mages have been switched then their magic will also be switched, as when Happy and Erza switched, Happy was able to use Erza's Re-equip magic and Erza was able to use Aera magic.