Severance

In the Legendaria, The Severance is a large-scale conflict between the Gods of Good and the Gods of Evil, as well as their respective forces on Ūnun.

Causes
Even during the Dawn War, the Gods of Good and Gods of Evil have rarely seen eye to eye. Their vastly different methodologies and moralities led to numerous clashes throughout their existence. With the conclusion of the Dawn War however, it seemed that there would be a chance for peace between the two groups.

Following the defeat of their mutual enemies, the Primordials, the Gods sought to create living beings to enjoy the world they created and had fought so hard for. Many of the gods birthed a new race in their image, becoming their patrons. When they had finished their creations, the Age of Guidance began, in which the Gods walked the earth with mortals, and helped them advance. It was a time of unprecedented peace, and all was well for many years.

Now, however, it is believed that the Gods of Evil had long planned to eventually turn on their brothers and sisters, an act that finally came to fruition with the Third Treachery.

Third Treachery
Shar, the sister of Selûne, was close with her sibling, but was often left in her shadow. With them each holding dominion over two polar opposite powers (light and dark), it is unsurprising that the two would sometimes argue or disagree. Eventually, their clashes got out of hand, and Shar broke away from her sister to live in isolation. It was during this time that she was approached by the Gods of Evil, united and offering Shar a place amongst them. She agreed, and it was up to her to begin undoing the work the Gods of Good had created.

Shar began by pushing her followers to war with the followers of her sister. Then, she cast the "Shadow over the World", plunging the planet into eternal night. Ūnun fell into disarray, and Shar's fellow Gods of Evil began their war.

War on Ūnun
The followers of the Gods of Evil began to destroy all which belonged to the Gods of Good and their followers, resulting in widespread conflicts across the globe.

Despite the darkness, Selûne was able to lead her people through the light of the moon, the celestial body most closely associated with her ever since. The Twilight Schism refers specifically to the war between the followers of Selûne and Shar that took place during the Severance. The two sides battled viciously, until Shar's supply of servants ran dry, and Selûne was all but victorious.

The Dragon Gods Paladine and Tiamat, long-standing rivals, called upon their worldly servants to do battle, resulting in the Dragon Wars, which continued even after the Severance. The Eternal Ten caused the most widespread damage across Ūnun, resulting in major losses for both.

The Astral Ward
Over many years, the Gods of Good were able to gain the upper hand against the Gods of Evil, and push them back enough to regain control. However, the Gods of Good mutually decided that the damage done was irreparable, and agreed that such an act must never be allowed to happen again. They created the Astral Ward, a powerful magic designed to keep the Gods from being able to ever again enter the Prime Material Plane in their true forms, including the Gods of Good. The Ward worked, and both sides were banished into the Astral Plane, never again able to seize control of the Prime.

Aftermath
The damage done during the war was inconceivable, and the fallout caused the mortal races to shrink into the First Age of Mortals; A dark age of regression and deterioration, until eventually the Age of Fey would arrive, under the influence of the Eladrin Empire.

The Dragon Wars raged on in the First Age of Mortals, before it is said that the only remaining Eternal Dragons: Zhilong, Paragon, and Khiros, did battle one last time. Zhilong and Paragon eventually defeated Khiros, but not without Zhilong and Paragon also losing their lives in the process. Zhilong is now seen as the essence of goodness in dragonkind; revered as a saintly figure among her ilk. Paragon is seen now as a symbol of wisdom and kindness, and typically thought of as continuing to guide the mortal races to this day. Some consider this a literal interpretation, with Paragon having survived the Dragon Wars, actually living amongst the mortal races, whereas others see him more so as being a spiritual guide. The Eternal Ten were themselves seen as quasi-divine by many, due to their immense displays of power, and status as the first living beings on Ūnun.