Annihilation event

Annihilation events are a phenomenon in Xenoblade Chronicles 3. They are destructive events that damage the landscape of Aionios.

Description
Annihilation events are not well understood by the people of Aionios. They are treated as a natural event that can occur without warning in any place at any time, generally preceded by a buildup of black fog in the area (which also jams Iris communication). Black fog is later used as a component of the Annihilator, a device that weaponizes black fog to trigger annihilation events at a distance.

Though an annihilation event is preceded by black fog, there is no advance warning before one finally occurs. A flash of light envelops a spherical area for a short time, followed by everything within the sphere vanishing completely. Anything on the edge of the effect is cleanly cut; matter above the effect may end up floating in midair instead of falling into the vacated space. Thus, within the space of a few seconds, a spherical emptiness appears in the landscape.

Story
The first annihilation event seen in Xenoblade Chronicles 3 is in the opening sequence where one destroys a middle section of the Urayan Mountains, followed by other smaller annihilation events in the surrounding areas.

Annihilation events appear to occur frequently in Eagus Wilderness. When the party goes swimming at Lake Rezzento, a body of water formed inside of a suspiciously spherical crater, Taion warns Noah that annihilation events occur often in the wilderness.

N later successfully tests the Annihilator weapon (which harnesses the power of the annihilation event) located at Keves Castle, destroying a portion of the Urayan Mountains. The Queen of Keves later targets Colony 4 with the weapon to "burn out the contagion". The aftershocks are felt to at least Maktha Wildwood, the party's current location. Ethel then sends Bolearis and later the party the data on the Annihilator through their Irises as the party volunteers to destroy it.

After P and O were defeated at Engardo Pass outside Maktha Wildwood, they stayed in their Interlinked form for too long, and consequentially, black fog began to build up around them. Fortunately, Noah and Mio manages to destroy the cliff where they're standing on, dropping them into the Great Sea, allowing the annihilation event to go off in a safe distance, taking P and O with it.