God of the sun, and light, and prophecy. Also of some other stuff. Leader and shaper of the western civilization. Appears as a strikingly beautiful youth.
Started out as a minor Greek god named Apollon. One of the sons of Zeus, who did his best to have a great many of them. In spite of what he did to his own father.
Zeus took great pride in him and his twin sister, Artemis, and they were both quickly promoted up the Olympus. When Helios, Zeus' brother, suffered his unfortunate accident, Apollon was there to fill his place, and it was in part to his own influence with the other Olympians that brought Artemis over as replacement for Selene, the goddess of the moon who was accused of harboring titans and destroyed.
For a short while he was happy, but eventually he got tired of being Zeus' puppet under Zeus' totalitarian regime on Zeus' bloody mount Olympus. He had some very fundamental disagreements with Zeus, and ended up defecting to Rome and forming his own posse of gods with their own nation. Thus was born Phoebus Apollo, and thus was born the Roman pantheon and eventually the Roman empire.
Before Apollo defected, he made sure he has a strong back. For this purpose he gathered allies, most of them were pretty young gods. The most noticeable ally was Jupiter, a warm blooded Thunder god and one hell of a fighter, who for his help received the official role of chief god. Jupiter, on his part, mostly behaves like the perfect puppet. He is highly resilient, formidably formidable, and not prone to asking questions.
In any event, Zeus went ballistic over the betrayal and executed Artemis in a fit of rage. It took Apollo several centuries and a whole bunch of thunderbolts to get his revenge, but he ended up slaughtering Zeus and every last remaining Olympian1) and a whole lot of lesser Greek gods and also his empire conquered their empire.
Apollo, perhaps for being a god of prophecy, was among the first gods to realize that mortals, in their growing numbers and advancing technology, are becoming a bigger threat to gods than other gods ever were. He started a massive and well coordinated effort to turn the Roman gods, and then all gods, into myth. Safer to rule from behind a vale.
This great concern he has with safety is sometimes labeled paranoia, or even cowardice, by short lived political opponents. These also tend to get hung up on his usage of Jupiter as a front, marking it as a sure sign of Apollo's deceitful and cowardly nature. But it's really about much more than that.
Apollo takes himself very seriously. He believes, at least superficially, that this planet belongs to the mortals, and that the gods must be a creative power and allow them to grow and develop. Knowledge of the existence of gods, he claims, saps people's will, hope and strength; not to mention their willingness to accept moral responsibility. He is a fan of man.