My nephew is playing an alchemist and wants to be able to take on the form of a demon or devil? Are there any spells similar to Fey Form or Form of the Dragon but based on granting a demon or devil form? I'm the GM and I'm fine with third party spells, archetypes, etc. I couldn't find anything like this on the d20pfsrd. Any advice would be appreciated. Thank you!
Ja Noi Aspect is close, with Ja Noi being an evil outsider that looks vaguely demon like (fiery-skinned humanoid possesses black eyes beneath the bony ridges of its brow). Geniekind for the same reasons, picking Efreeti gets you cosmetic horns and red skin.