Forms

When you change your own or another creature’s form using a spell with the polymorph descriptor, the target’s original form (referred to as its true form) is used to determine anything that is not explicitly changed by the spell.

When you learn a spell with the polymorph descriptor, you design a number of specific forms (as determined by the spell) known as polymorph forms. Each of these could be based on an extant creature, or they might be a product purely of your imagination. You can thereafter cast the spell to change yourself or another creature into one of your predetermined forms. These forms might be specific to you, each having a unique look that remains the same from one casting to the next (potentially even mimicking a specific individual), or they might be generic (so you use that form when you change into a creature, but the target’s appearance is different each time within the norms for that creature). You cannot, however, transform a target to have multiple forms at one time (so you couldn’t, for example, transform a single creature into a creature with the swarm subtype).