Lucifer, the first exiled angel

Not wanting to extol Lucifer, the grandest egomaniac of existence, the observer chooses to make this exposé brief. 

The one now called Lucifer was one of the twelve known as Archangels, the first wave of angels created by God after forming the first angel later known as the 'Son-of-God,' who then became leader of the rest.

 Lucifer decried God for his own fiefdom as he wanted to be an ultimate god himself, yet since God is everything and there is no place without God, the first angel figuratively threw out the universe as a space-time continuum where Lucifer could play-pretend there was no God but himself.

Arriving on this world as it was forming, and wanting to be it's master, he worked all the plants and dinosaurs to his liking, and raised via what we call evolution, a civilization of humanoids to admire his mettle, styling himself as the god-of-the-sun, hence the name Lucifer, which means 'light.' This he did  to jealously copy the actual prince-of-light-without-shadow, the first angel whom we now know as the Son-of-God.

The whole universe may have been for Lucifer to play in—to be the god of—and it's possible that he cultivated other civilizations elsewhere within it, for the "Son-of-God" is reported to have said he had others elsewhere to attend to. But this is a 'maybe,' for that statement has no corroboration

But either way, with opportunity to recant his selfishness and return to heaven as a trusted colleague, or to totally renounce God and eventually be unmade, it's apparent that choosing against God sealed not only Lucifer's fate. but those of who later sided with him, since any who blasphemes* God are no longer allowed return to paradise.
* "Blasphemy" is the word used for totally renouncing God. Blasphemy the only line crossed against God that can't be forgiven, and it is not so-much a mental choice but one of the heart.
God's Chief Angel—the Son-of-God—told us himself that although one can blaspheme either he or other angels and be forgiven, blasphemy against God cannot be forgiven (e.g., Mark 3:29) — marking blasphemy as the only irrevocable crime against God.

After Lucifer was cast from heaven some 13.7 billion years ago, as scientists recon the Big Bang as occurring, it was relatively recently that one-third of the billions of angels God later created also considered leaving God. For their wanting to be free of God, He installed them into Lucifer's civilized humanoids about 6,000 years ago, as true avatars, beginning history as we know it.

And although as most had not blasphemed Him but only considered leaving -- God exiled them to earth for a great cull, to see who amongst them would eventually blaspheme God (as Lucifer had eventually done), and who would not. Therefore it was up to the first angel—their leader—to arrange return to Heaven those who wanted to go back. Which flummoxed Lucifer.

We win

To reiterate. we people ARE God's later fallen angels. We were created as mystic beings—minor gods or demigods—to live in human bodies on earth sans our former abilities.

For you see, having claimed this earth for himself, and having raised the humanoid bodies we now occupy, Lucifer wants to get as many of us as possible to join him for that final dance-into-the-fire, spelling his and our ultimate demise.

To that end he'll even stoop as low as pretending to be the ultimate God and Son-of-God just to mess with us.

Now, be sure of what you're getting into before reading further. You may learn more than you want to know, for as the Son-of-God reportedly told us that we'd be responsible for our knowledge.