702.140b
As a mutating creature spell begins resolving, if its target is illegal, it ceases to be a mutating creature spell and continues resolving as a creature spell and will be put onto the battlefield under the control of the spell’s controller.
As a mutating creature spell begins resolving, if its target is illegal, it ceases to be a mutating creature spell and continues resolving as a creature spell and will be put onto the battlefield under the control of the spell’s controller.