Ethereal's not the issue. They have to be like the Archangel Phanuel anyway, whom I described as ethereal in v1. However, angels have the ability to make themselves appear solid. If I remember correctly, it was (solid) angels who were threatened sexually in Sodom (or Gomorrah?). Also, a small force of solid angels will participate in the final battle on Megiddo against a horde of Satan's corporeals in book 3.
Angels can appear as either ethereal or solid. Demons lost the latter ability when they were cast out of Heaven, which is why they have to take over dead bodies to be solid, whereas angels don't. One advantage of demons taking over dead bodies, though, is that the dead bodies protect the demons from the effects of holy ground, otherwise they'd never be able to enter a church as they do in my book.
The thing I was asking about is what the demons should look like. Slightly rotting human corpses is what they take over to become corporeals, so I'd like their spirit form to look different: some hideous transformation from beautiful, humanlike angels to some highly corrupted version. A shriveled form and stooped could be two attributes. Red eyes and (ethereal) black bodies might be two more. Something reminiscent of orcs or goblins or gargoyles?
I'd like something that is very easy to describe and easy for the reader to picture. Perhaps they have (spiritual) bodies like bats and faces like black dragonfish. The advantage of batlike bodies is that bats can fly as can demons (they still have wings left over from when they were angels, but they look gross (singed/blackened, holes in them, shriveled)).
I wonder if they should have some fluids oozing off their nude/hairy bodies that drips from the spirit world to the physical world. Imagine a scene where a character feels something drip on their neck and looks up to see a scary-ass demon flying down at them. (Angels make themselves appear clothed, whereas demons, with their hairy, batlike bodies, wouldn't need to.)
Safe for work:
https://www.thoughtco.com/the-worlds-sc … ls-4105205
Stuff like that.
Dirk