To modern eyes, medieval images of demons may appear comical and quaint. You should realize that these images, and the understanding that Christian demonologists had about them, were merely unsophisticated attempts to come to terms with real, perceived phenomena of daily life.
Demons in one form or another have been a constant fixture of folklore and myth in all cultures around the world since the dawn of history. While this is not proof that these folk beliefs are literally true, it suggests that a core of truth exists that has sustained and defined the myths of demons over the centuries. It is nothing short of intellectual arrogance to leave unexamined so universal an aspect of human experience.
“If he was as beautiful then as now he is ugly,
when he lifted his brow against his Maker, well
must all grieving proceed from him. Oh how
great a marvel did it seem to me, when I saw
three faces on his head! ... Beneath each one
came out two great wings....They did not have
feathers; their mode was like a bat's....With six
eyes he was weeping, and down three chins
dripped the tears and the bloody slobber. In
each of his mouths he was breaking a sinner... “
The other shape If shape it might be call'd, that shape had none,
Distinguishable in member, joint, or limb;
Or substance might be call'd that shadow seem'd;
For each seem'd either; black it stood as night,
Fierce as ten furies, terrible as Hell,
And shook a dreadful dart; what seem'd his head
The likeness of a kingly crown had on.
Satan was now at hand; and from his seat
the monster, moving onward, came as fast
with horrid strides; Hell trembled as he strode."
John Milton’s Paradise
The truth is that demons are more likely to appear in attractive. They love to masquerade, so even Christians are fooled by them. Paul warned them that even "Satan himself masquerades as an angel of light. It is not surprising, then, if his servants masquerade as servants of righteousness" (2 Corinthians 11:14-15).
In traditional black magic, demons have usually two shapes : a monstrous one and a pleasant one. The pleasant one can be a beautiful woman or an elegant good-looking man.
When a demon is of high authority, it appears in human form. Demons in animal forms are of lesser importance. Still less in rank are demons that come in the shapes of insects or plants. And last in importance are demons that appear as objects. regardless of what is claimed for him.