Geological / environmental event
The earth began to shudder and extreme cold blew in as though from nowhere, bringing snow and harsh wintry winds. The ground split and sundered with pieces driving into one another, causing it tower towards the cold sky as if grasping for life. Mountains rose from the frozen lands for miles around, leaving the lands devastated and for only the most persistent of creatures.
On this day, the Frozen-Teeth mountain range came into being. At it's center, the Leyline of Winter stands out among the others in the range.