Shape shifters One form of limitations could be that the shapeshifter needs an animal pelt, such as the selkie skin, or forms of the werecreature myths. In some werecreature myths, the person could only shift with the removal of clothes, and only become human again by putting on their clothes again.
"Eton," I whispered. "Lower your voice. You'll wake them." Eton stared at me confused. "Wake who? We're the only ones trapped in this cave!" I pointed down the hole that had been exposed when the cave-in happened. "Them."