Geological / environmental event
Dark skys
Following the impact of Martilumok on Zinyor, dark clouds rose above the land, effectively blocking all sun rays, especially infrared. Following, Xiantar cooled down, the surface was covered in snow and ice to large degrees. Many cultures vanished. Some races did not survive this period, others hid in the earth's bones, others miraculously survived in the open. Myths and legends, history from before this enourmous impact, all vanished. There is little to no knowledge on who and what populated Xiantar before.