>>538455745
There's no historical source image for the mark of Cain, you kinda have to make it up, or just base it on something else.

In the book Demian, Demian himself argues that the mark wasn't an actual curse from god, but maybe a face deformity that someone in the past had that made them stand out, or maybe a scar, and because they were highly competent, or strong, and nobody could fuck with them, those around the person made up a lie about how that mark was punishment from god to isolate them socially, since they couldn't win in a straight fight, most likely due to envy.