Interesting points Mercule, and ones that are addressed in the game. Demon doesn't fall in completely with Christian theology- it is based on it, but the game assumes no real world religion has all the details of the divine war and fall. The angels were tasked with the development and nurturing of humanity by God, but never to reveal themselves to humans, and never interfere. The rebel angels loved humans as much as God (because they were told to), but it frustrated them that they were not allowed to interact with them. Then, one of the angels of the house of the stars foresaw that disaster would come to humanity, so the rebel angels decided to act. They revealed themselves to humanity, professed their love, and told them they would act as humanity's servants and protectors. Eventually a big war followed with the divine forces, and at first the rebels had the upper hand. But over time, the divine host gained strength, and the rebels were cast into Hell. However, Lucifer wasn't cast into Hell with them- and no one knows where he is. Additionally, as time passed, some demons vanished from Hell, apparently summoned by mortals to dot their bidding, and these demons later became Earthbound (basically bound into a relic on earth so they would not be subject to imprisonment in Hell again). When the game starts, the prison of Hell has cracks in it, allowing some demons to escape and come to earth, possess mortals, and pursue their agendas. While some demons want to find redemption with God, others are still loyal to Lucifer and his cause, and seek to find him, then finish the war with Heaven. Others were driven mad over the millenia in Hell, and want nothing more than to punish humanity and make them pay for the loss in the demon's power. Still others aren't so sure that they aren't menat to play a more important role in the days to come, and seek to understand why God would allow his perfect prison to break. Finally, some seek to establish a paradise on earth for themselves and those loyal to them.
Its an interesting take on mythology, and has made for some really memorable RP experiences so far. Nobody is completely in the right or wrong- God is not protrayed as completely noble, nor is Lucifer shown as a raving rebel. The other thing is that the demons depend on human belief and faith, and even in those that are angry at humanity now, they still feel the love they were ordered to feel for humanity. Very cool game that challenges many preconceptions and is very RP intensive.