Exactly what it says on the (dramatic) title.

We always hear about Biblically accurate angels: the burning wheels with tons of eyes, the strange looking creatures that sound like they come from the anime "Evangelion", the cherubim with 4 faces, but I had a thought while watching The Exorcist: Believer (it was....not good for anyone wondering. At all. The disrespect Regan's mom had towards Merrin and Karras after they died saving her daughter was baffling to listen to, especially...but i digress) a couple of days ago, specifically, if that's how the demonically possessed are said to more or less act in the Judeo-Christian scriptures, or if they're they completely different to what we see in movies and games. I'm guessing it's more than likely the second one, right, but I'm curious about the details like the signs someone's possessed, the demon's endgoal, and what they look like, basically everything you can gimme to sate this curiosity or to send me on a rabbit hole, if you'd be so kind?