Rift

Rifts Rifts appear at "random" and can often fundamentally change the landscape where they appear, affecting large areas or sometimes small sections of the world.

The largest recorded rift was during the formation of the Sea of Glass, which decimated Shakar.

Rifts - Out of Game
They can add or remove features, typically creatures and structures, and take them to an unknown plane or alternatively they can place said features from an unknown plane onto our world.  When a rift opens, it is directional, meaning things can either come out of or enter a specific rift, not both.  If a player would like to have a rift involved with a plotline they wish to run, they must check with the plot team first.