Gint orginally created Kyrith in the 80's for his RuneQuest campaign after inspiration from the movie Fire and Ice. Not much remains from that movie except the idea that a large glacier dominates the north and that the campaign takes place a little sooner after an ice age than our present civilization.
Gint returned to Kyrith when the D&D 3rd edition rules came out and many people wanted to play. At first he started creating a new world but soon realized it was looking a bit like Kyrith. Some of the basics of the Kyrith mythology and history remained but much changed as it became more D&D.
