The Kitin Wars
The kitins set out on a crusade to obliterate all traces of hominkind. Many homins were able to escape through the teleportation 'rainbows' leading to safe haven in the Prime Roots of faraway lands. Kami and Karavan forces did their best to give homins safe conduct to the rainbows until these too were destroyed by kitins.
Remaining homins could but flee into the wilds where they were forced to live nomadic lives in constant fear of kitin attack. A Karavan task force was eventually sent in to counter the arachnid onslaughts.
War ravaged in the ancient lands for two long years until at last the kitins were forced to retreat back into the depths of Atys.