He calls himself Lucifer and is actually a very old demon possessing a canine’s body.

The demonization of the body has partially happened already, explaining his unnatural look.

Sometimes when demons live old enough and become very powerful, their soul remains on earth even when their body becomes unusable. This sometimes occurs among other living creatures too but the difference is they become ghosts, aimlessly wandering around and forgetting themselves. Powerful demon souls, however, still remember who they are. The continue their life on earth they try to posses bodies for souls are unable to do anything but float around.

Lucifer used to be a female bodied demon who was both feared and respected by humans and demon alike. The demon possessed a male dog's body and has settled down just well, enjoying his new body. Due the demonization that slowly starts after the body has been possessed, Lucifer can even alter his body a little. For now he is able to make his hands to resemble that of a human's and with time he is probably capable of making his body more human-like too.

weeehhhh I was making warmup sketches on train and I usually draw canines out of habit but?? he was not supposed to become a character. What happened. I don't know