Metaphysical / Paranormal event
Auril, the Frostmaiden, weaves a spell across Icewind Dale that prevents the sun from rising across the region. This plunges Icewind Dale into a perpetual, dark winter that threatens the entire region.
In 1495 DR, Auril's avatar was destroyed by a group of adventurers on the island of Grimskalle, ending the Everlasting Rime.