Doomskar

A Doomskar is a collision of the realms of Kaldheim which causes earthquakes, destabilization, and total chaos. With it, inevitably, comes war and chaos. A time of great suffering.

Description
Although each realm is distinct, they are all in constant motion around the World Tree, and sometimes they overlap. Such an overlap is called a Doomskar, and it's a violent, explosive event marked by world-altering earthquakes and geological destabilization. Inevitably, the inhabitants of the overlapping realms come into conflict.

Influence
A Doomskar is essentially a mini-Ragnarök.