Hello! Thanks for the big reply. I've been thinking on it since I got this response and I still do want to run with my idea of my human character carrying a demonic curse passed down from an ancestor (also human), and being mistaken for dragonborn instead due to how long it's been since the curse and Sidurgu's birth. His family's taken pride in it since it's made them look like dragons and forgotten the real reasoning behind their appearances. I'm still thinking of what else could have accompanied the curse's physiological effects, like maybe an increased inclination for forbidden magics (he's a practitioner of such in canon), or something else.

Being considered something he's not and having to deal with hate and attempted assassinations over his appearance a giant part of Sid's development in canon. Without that, he'd turn out to be different from the essence of the original character and I don't want to stray far from it despite Usir being an AU, I hope you understand!

edited to say i decided on beastfolk after talking to a friend for some outside help on history building!