Ragnarök

Ragnarök was the final conflict and an extinction event before the Great Division (also known as Big Bang) that result in the near-extinction of multiple species and the complete extinction of the mortal Vanir, Aesir, and Jötnar.

Prelude
Following the end of Fimbulwinter and Loki's Vengeance; Ragnarök began immediately and began with the forces led by Odin trying to prevent the end of world while Loki and most of his children fought to ensure that Ragnarök would go according to plan.

War
The fighting was took place mostly in the Midgard section of Earth and the area was almost completely devastated from the fight. Rivers became oceans, mountains became plateaus, and cities became sinkholes. Trillions of species that weren't involved were killed in the crossfire, but the majority of them were spared and were able to escape the war.

Aftermath
The war/extinction event brought an end to the Proto Period and began the Hadean Period. the Original Universe becomes the Hub and all evidence of the Proto Period was either scattered across the Multiverse or stored by the Patrolman.