Lucifer had a, slightly, different physical appearence before being cast out of Heaven.
The only things that were similar was everything bellow the head. Same torso, arms, legs, etc.
But, his head was the design of a Biblically accurate angel, and he chose to present himself with two black eyes with white irises and a black mouth with white teeth
He lost that bit of himself when cast out of Heaven, it practically burnt off him when he fell down into Hell.
Now, he’s only able to assume that form for a very short amount of time, mostly used for intimidation displays more than anything else, as it causes him physical pain to be like that. After all, his sinful body is being directly bathed in the Heavenly light that radiates off his once naturally angelic head.
The second situation is if he is directly under the light of Heaven in the Magne Estate, that allows him to stay in the form for as long as he wants, but only if conscious. Even then, he refuses to do it as, like I’ve said before, he wants nothing to do with God anymore.
If bathing in the light of God’s palace is what allows him to keep up his angelic form with no struggles, as if God himself is looking down at Lucifer and reminding him of what he abandoned, then he wants nothing to do with it.
