I have experience with demons of Goetia.

In Dictinonnaire Infernal and Pseudomonarchia Daemonum, they're portrayed as horrific monsters. This is, however relative. It all depends on how you approach them. If you approach with intent to "control them", they will appear as monsters. If you approach them with utmost respect, they appear humanoid, and they are beautiful. And they're not intrinsically evil. That is also relative.

Are they representation of ones own psyche, or something external, I don't know.