Humans know about the incident surrounding Belials eventual casting out from the Angels order. The story is simply known as the story of 'Adam and Eve'.
Belial was one of the Seraphim under Arch Angel Michael, and a personal guard to Jehovah himself. As such he was privvy to the disgusting and lavish selfishness of God.
Heaven became a more luscious and green place the closer you got to St Peters Gate, but became more barren and poverty riddled the further away from the 'emerald city'. In one such barren shanty village two scorned angels named Adam and Eve bore three sons, two you may have heard of; Cain and Abel they were named. Both strong Angels, farmers and defenders of the village to where they were raised.
The third son was named Seth. He was born crippled in the mind and as such became a peril to himself, his affliction meant he never fully learned the difference between right and wrong. So it came that God had him executed for stealing a loaf of bread from the back of a cart intended to arrive at St Peters Gate two days later.
Seth was simply hungry, and the sight of two hundred loaves of bread drove him to simply pick one up and walk home with it. Instead of taking the bread from the boy a member of the guard simply shot an arrow through his head on Jehovahs orders. Irony would have it that all bread was spoiled before it reached the gates to Jehovahs Palace.
Belial was the Angel instructed to inform Adam and Eve that Seth had been savaged by a rabid boar and torn to pieces mercilessly by the crueltyu of nature, and that there would be a tribute to him held in the Palace halls.
So as the serpent persuaded Eve to eat from the tree of knowledge, a sickened Belial delivered a different message. He told Adam and Eve the truth and their outrage caused them to be banished from heaven, taken into Limbo.
Belial fled the judgment that would have been his, he was through with the guard duties, and he was through with the decadence of Jehovah.
The story became warped to include Apples and Gardens and knowledge. Eve was balmed by the humans for all their afflictions in childbirth, and Adam for the toiling of the field necessary, for no more would the mythical Mana be so willingly given.
But the truth was, Belial had decided to do the right thing.