Lucifer

First, to clarify and for anyone wondering, this is the Lucifer from the comics Sandman and Lucifer. He was one of the first two angels created (the other was Michael) and he helped to create the universe; he's especially known for having lit the stars. He walked out on Yahweh and fell, became ruler of Hell, etc., and is currently retired and running a piano bar (though sometimes he fails more at retirement than he intends).

In his canon, he's one of the most powerful beings in existence - he kills several gods and destroys the Mansions of the Silence just by walking there. While most of this won't apply, this does mean he needs permissions for some of his abilities. So here goes:

1.) In Lucifer's canon, he meets: Endless, gods, spirits, a sentient Tarot deck, faeries, angels, demons, golems, etc. and he always seems to know what they are and what they do. So my guess is that in most cases, if you give your permission, he'd recognize what your character is and maybe have some idea of their abilities if they're somehow supernatural.

2.) Among other things, Lucifer can and will bestow nasty curses when angry. In canon, these are permanent, but I wouldn't do that to you - any curse would be temporary. Are you okay with him cursing your characters should the occasion arise? (Don't worry - I will also discuss specifics with you if it comes up.)

3.) Along with recognizing what things are, Lucifer recognizes magic, so he may notice any illusion on your character, if they're cursed and the nature of the curse, and if they have magic items of some kind (and maybe some of what the item does).

I think that's all for now!