Humanoid demons look pretty much like any other humans, except they have an enormous connection to magick with great powers. Lillith is a good example of a humanoid demon. Some practitioners can summon demons, but that practice has fallen out of favour in modern times. Practitioners will sometimes use familiars to perform magick. They can channel the magick through the familiar and thereby yield a greater level of magick.
Any small animal can be a familiar, although the cat seems to be the favorite of choice.
Ghosts There has been no formal discussion of ghosts. However, we have seen some. Sebastian Sebo, the nickname Ruth has given him, is a cat familiar, but not an ordinary one. He can actually communicate with other magickal beings. It s sort of a language that he has.