Kincarly

A period of time on Lyrend where there was massive volcanic upheaval, tsunamis and weather pattern shifting, as if the entire planet had been rocked. (It had.)

It came about because the Riders and Vessels moved the planet. It killed thousands of them (and thousands below died as well) but was seen as necessary to move the planet from risk of the continual Dragon attacks.

Killed thousands to save millions.