Skirting The Dodgy Path
The Riftwar was a decade-long war which culminated between two worlds, Kelewan and Midkemia. The major combatants were the Tsuranuanni Empire and the Kingdom of the Isles although other factions supported them, such as the Thuril and the Cho-ja for the former, and the Elves and Dwarves for the latter.
The war begun when Tsuranuanni invaded Midkemia by creating rifts between the two worlds; as a result of a series of political intrigues between the Tsurani political parties in the Game of the Council. The apparent cause of the invasion was the lack of metals in Kelewan, and their abundance in Midkemia, specifically the Grey Towers.