Illumination 3 Page 40 (Patreon)

If there's one thing I want to get across about the world of Skin Deep, it's that magic is unpredictable, even when very powerfully magic creatures use it. Sure, the sphinxes invented the medallions, and did all they could to figure out how it would last, but at this point in the comic the medallions were still new, so any theory they had about how they would work was still theory. And magic looooooves to go "hah hah you thought I would do what now??"