Adjustments from Canon
In here, please find some background information that will be necessary to add to your knowledge of the canon in order to go along with some of the plot of the game. Not much is different but note that there will be heavy influence from Paradise Lost in this game (as is with the canon of Demon the Fallen).
Age of Wrath
The beginning of the Age of Wrath begins, as it were, with the rebellion of Lucifer and a third of the Elohim. The Morningstar’s decision to defy God is the spark of the Age of Wrath. However there are a few adjustments in the story of the Great Debate.
The Debate and the Fall (Abdiel the Eveningstar and the Betrayal)
Per Paradise Lost, Abdiel was the Seraph that betrayed Lucifer to God. In “Fallen Idols,” we hold this to be true. Here is the story you might hear if you remember the Fall.
“During the Great Debate, when Ahrimal showed fellow Elohim the future he had beheld for mankind, Lucifer the Morningstar appeared in radiant light. To his left was Abdiel, the Eveningstar and Seraph of Sunset, his constant boon companion. She too glowed with light, though softer and echoing the First of the Heralds. Garbed in light, her hair fading from a reddish brown to a rich orange red and her indigo blue eyes bright, she walked in silently besides Lucifer. Silent, she watched the debate with interest but allowed Lucifer to speak for both of them.
“That is, until the end. As Lucifer proclaimed his plan, Abdiel turned and stepped away, something she had never done in all of creation’s memories. Her eyes cast a gaze over the gathered Elohim and, finally, she spoke.
“It did not happen like in Milton’s story. She did not raise her voice to Lucifer. No, she spoke to all of the angels present but, most of all, to her other half, the Morningstar.
""I will not let you do this," she said, her voice dark. “You do not know what is true yet look how proud you are. The Maker commands us to Her will and yet you think you are capable of going against Her? Free will was not our gift. That was Hers and Hers Alone. It shall be by the morning star that you will finally see war.”
“As Usiel and Lailah proclaimed that they too would not rebel, Abdiel rose in a flash as the sun set over the world. No, Usiel and Lailah only followed in her wake and all knew very well that Abdiel headed for the highest of heavens. Though we do not know what she said to the Maker, we know that it was her act that started the war.”
Age of Wrath, Time of Babel, and the Shattering
The first battle in the Age of Wrath had been between Michael and Lucifer, but the first strike on either side had been from the Eveningstar, heralding Michael. With her spear in hand, she struck Lucifer and the war between angels began. Still, Lucifer was victorious in the first battle, aided by Madisel’s Scythe, against Michael who was too new to his power. The war, however, was in its infancy and there was no such idea of harm yet in the rebel’s hearts.
Further still, at the end of the first battle, Michael gave his curse to the rebels, naming them what we know now as the Houses of the Fallen. God then Herself exacted Her wrath and rendered the first world to ruin.
The formation of the Legions would only be the beginning of the end, as the differing ideologies marked dissension among the Fallen’s ranks. Lucifer’s Crimson Legion led by Belial, Abaddon’s Ebon Legion, Dagon’s Iron Legion, Asmodeus’ Silver Legion, and Azrael’s Alabaster Legion—all originally were part of Lucifer’s Grand Plan but no one could have expected the treachery the fracturing would cause.
It was not until the First Murder that the Fallen knew bloodshed. Caine’s murder of Abel unleashed atrocity for all beings and it was through this that the Age of Atrocities began. The Legions broke and the war became riddled with blood and gore for mortals and angels alike. The Long March was Lucifer’s last bid to continue the plan the rebels had taken at the beginning: a kingdom of paradise. So did the Morningstar begin the Great Experiment, the Ten Watchers sent out to teach humanity knowledge.
Still, this caused even more dissent and the Nephilim were born to murder the Ten. Thus came the Shattering, humanity buckling under the weight of divinity, destroying Babel and the First Tongue while Lucifer battled the Nephilim.
Thus did the Great Experiment come to failure and Michael would destroy Genhinnom (the Black Cathedral) and chain Lucifer with fire and steel. The Fallen were pushed to hell and the rest is history.