This may be more of an art history question than anything else but that is what I am here to find out!
I was curious about how depictions of the three (or any other Christian demons/evil entities) came to be represented the way they are today and their possible source material.
Do we know the earliest works depicting the religious figures? And how/why they were represented in such a way?
Disclaimer: not religious
Not a subject I have researched tremendously, but medievalists pretty much depend on Jeffrey Burton Russell's research that concluded the visual depictions of Satan materialized in the west in the 5-6th century CE. Here are the books to read if you want to dig deep into all things Satan, including tracing visual depictions and characteristics:
I lightly caution against taking all his theories of origins of images with some skepticism, his breadth of knowledge on source material was amazing but he was sometimes very formalist. Check my previous post on the devil's pitchfork for some discussion of that.