Anu

Anu, or God of the Bible, was the very first being in Creation. It was Anu who fought the battle with the Prime Evil Tathamet, their struggle leading tot he creation of the universe and also the births of Heaven and Hell, Elder Angels and Demons. He was also the former leader and creator of the Four Great Seraphs, Ten Seraphs, and the Angels. He was also the creator of the Holy Swords and the Sacred Gear System. Despite his death, God’s will resides in the strongest Longinus, True Longinus.

The Dawn of Time
In the beginning, there was but a single, perfect pearl, in which Anu resided. Anu was the sum of all things: good and evil, light and dark, physical and mystical, joy and sadness—all reflected across the crystalline facets of its form. And, within its eternal dream-state, Anu considered itself—all of its myriad facets. Seeking a state of total purity and perfection, Anu cast all evil from itself. All dissonance was gone...for a time. These discordant parts formed into the being Tathamet, the first Prime Evil. Though separate beings, Anu and Tathamet were bound within the pearl. There they warred against each other in an unending clash of light and shadow for ages uncounted, neither gaining the upper hand. At last, their energies spent after countless millennia of battle, they delivered their final blows. The energies unleashed by their impossible fury ignited an explosion of light and matter so vast and terrible that it birthed the very universe itself. Many refer to this as the Big Bang.

The only witnesses to their eons-long struggle were Ophis and the Great Red, who were extremely, extremely young at the time. Back when they just started to become aware of their surroundings.

The Eternal Conflict
Anu however survived the battle, albeit with mortal injuries which would never heal and slowly kill him over time, including a missing eye which formed into the Worldstone, lying at the heart of Pandemonium, the scar of the universe's violent birth. His power had also considerably waned due to the neverending struggle against the Dragon, one that would continue to decrease over time for as long as he lived.

After the battle, he then cast Tathamet's blackened, smoldering husk spiraled into the lower darkness of reality. From his putrid flesh arose the realms of the Burning Hells, and the race of demons that arose from them like maggots from a corpse. Additionally his seven heads spawned the Great Evils. The strongest of his maws gave birth to the three Prime Evils, while the four lesser heads gave birth to the Lesser Evils.

Anu knew, wounded as he was, that he could never face the unending threat of the demons. Thus, in an effort to combat against them, he decided to make a realm of his own with warriors that would act as the counterbalance to that evil. For reasons unknown to this day, Anu tore out his spine and flung it into the primordial darkness, where it slowed and cooled. Over countless ages it formed into the Crystal Arch, around which the High Heavens took shape and form. It is from this arch that the Elder Angels come into existence. The purest of these Elder Angels, archangels comprised of Anu's quality traits of valor, justice, hope, fate, and wisdom, formed together to become the Angiris Council. Anu then took command, with the Council as his advisors and second in command.

Thus the Eternal Conflict between the High Heavens and the Burning Hells for the fate of the universe began.

Departure from the High Heavens
The events of the Sin War had ensured that the Eternal Conflict would take on a new paradigm, one that boded ill for the Angiris Council as much as the Prime Evils. The ceasefire did not sit well with Imperius—robbed of an enemy to fight, he became something of a "legalistic tyrant." That Tyrael had not sided with him at the conclusion of the Sin War was another thorn in his side. Furthermore, Tyrael would continue to act on his own, aiding humanity despite the edicts of the Council. Auriel continued to act as a bridge between the two angels but Malthael was another story. It is said his mood darkened after the creation of Sanctuary. After the destruction of the Worldstone, he simply vanished. In light of his absence, Imperius took over leadership of the Council, where division continued to exist between him and Tyrael. Anu however was also another story. Seeing how much damage the Worldstone, and by large the Eternal Conflict had caused to Sanctuary, Anu felt pity for the first time and decided that he can no longer sit by while humanity suffered. Thus, he announced that he would leave the High Heavens and passed the ownership and rule over to the Angiris Council.

Once he arrived to Sanctuary, Anu, taking the simple name of God, decided to rebuild it from the damage the endless wars had caused. He first put mankind to sleep and buried them beneath the earth before drowning it in darkness, cleansing it of the corruption and damage it had sustained. Then, as told in the Bible, he rebuilt the earth in six days and nights and rested on the seventh. To ensure that Sanctuary, now named Earth, was properly taken care of, God created the Lower Heavens and the Young Angels before he next woke up mankind.

Over time, God came to care for humanity and adopted them as his children despite knowing he did not create them. During this time, he understood why man and the nephalem were so feared by the Elder Angels and the Demons thanks to their innate and dormant power within. Thus when the Great War eventually sparked, God prioritized the safety of mankind out of fear that the Three Factions and perhaps other forces would forcefully exploit their power for their own needs.

The Great War
The Three Factions started thousands of years before the start of the story after the Biblical God cast out Angels that opposed his teachings, creating the Fallen Angels who inhabited in the Underworld alongside the Devils. Unlike other supernatural groups (Norse Gods, Hindu Gods, Greco-Roman Gods, etc.) which were apparently more or less independent of each other, these three factions were all interconnected. Together, the Three Factions spawned the Judeo-Christian religion, and became part of the Bible.

The Three Factions of Angels, Devils, and Fallen Angels eventually warred against one another under the leaderships of the Biblical God, the Four Great Satans, and the Fallen Angel organization, Grigori, led by Azazel, in a conflict which came to be known as the Great War which continued for an unknown period of time.

Unbeknowenst to all, even to God, this was all part of a plan concocted by the daughter of Mephisto, Lilith, to weaken/wipe out the Three Factions and enslave mankind to her will. God commanded the Lower Heavens to defend mankind from the Fallen Angels and Devils, both of which sought humanity's inherent power of the nephalem.

Death
Towards the end of the Great War, God realized that there was not much time left before he succumbed to the mortal injuries he had sustained eons ago against Tathamet. Not wanting to simply lie down suffering in bed, God decided to entrust the future of Earth over to mankind, believing that one day, should the Prime Evil returned, all races, including the Elder Angels, will unite against its evil. Leaving the Lower Heavens, God departed to Pandemonium, where he found the missing archangel Malthael, who had become the Angel of Death. God then commanded for Malthael to take his life, which the Elder Angel complied without hesitation and without remorse.

Thus God was slain in front of the Three Factions, his will transferred over to the True Longinus. Malthael then earned his nickname Slayer of God.