The Demon Spawn War (8972 GE - 9493 GE) was much more than a conflict between the Covenant and the Abysseal Hegemony. It was also a time when great leaders felt the need to become something greater. They felt a pull from beyond the Mortal Systems, a path to becoming a Higher Power.
Behind all this is Divine Energy, the stuff acquired from having devout followers. Have enough divine energy, become a god.
The Temple of Ascension is protected by a Modron army. They allow only those with divine potential to enter the temple. This divine potential is the accumulation of divine energy from mortal followers.
The Modron Templars, for hundreds of miles in every direction, keeps the peace, and the sanctity of the Temple of Ascension. Sometimes they fail. On 27 Dreamer 984, the villainous Set raided the temple just as Jurmalon was about to be ascended. Set was taking revenge on the Elderaunts, capturing him for the great Khazarkar defeat at the Battle of Satheon (1016). Taken to the Black Chariot, Jurmalon has never been seen or heard from again.
In the Horgon Era, the Saints of Maen used their Torc of Maen Grirngrim along with the help of others, becoming Higher Powers. Their torcs, forged by a fel being of the Creation War, interfered with this Ascension. It made them immortal, made them vessels for divine power, but also turned them into undead-like things, one became a thing of dessicated flesh and bones, another of dark wisps, and one a creature of shadows.