Intersection

The Intersection is an apocalyptic event in Xenoblade Chronicles 3. It is an universe wide annihilation event that will destroy the worlds of Bionis and Alrest.

Prelude
In the distant past, the two universes that comprises Aionios were one. In the year 20XX, Klaus activates the Conduit during an attack on the First Low Orbit Station by the Saviorite Rebels in a last ditch effort to escape from the war, splitting the one world into the world of the Bionis and the world of Alrest respectively, as well as flinging each half of his body to each world.

Xenoblade Chronicles 3
Years after Klaus's death in each of the universes, the worlds begin to draw towards each other, but will destroy each other if they collide as they are made of opposite matter. By communicating with each other, via light, both worlds made contact for the first time. The queens of each world, Melia, and Nia each constructed each half of Origin as an ark to reboot the lives of each world once Intersection begins.

When the worlds fused, however, the reboot process failed due to Z and Moebius interfering and capturing Melia to gain access to Origin and take it over, trapping the world in an endless cycle of life and death to keep the worlds frozen in time. Thus, Aionios was born. Despite the cyclical flow of the Endless Now, the two worlds still interact on occasion, leading to annihilation events, smaller portents of the looming annihilation, slowly whittling away Aionios. Nia later tells the tales of the Intersection and the creation of Aionios to the party after she wakes up at the Cloudkeep. After Z's defeat, Origin is reactivated, and the constituent worlds of Aionios separate. After an unknown time, the Intersection would come to pass unimpeded. Afterwards, Origin would perform as expected and restore Bionis and Alrest, and all the people of either world. Then, both worlds would combine again, this time without annihilating one another.