From the introduction: For centuries, genies from the greatest cities on the Planes of Earth and Fire have waged a bitter war. The shaitans churn out soldiers from their vast stone barracks in the Opaline Vault, while the efreet enact cunning plots in their fiery palaces in the City of Brass. The conflict has raged along the border between the planes, where rivers of molten stone flow into fields of lava and burning cinders rain down upon deserts of ash. Many of the roads that cross these dangerous regions have become the sites of tense standoffs that occasionally erupt into battles, making travel along the roads more perilous than braving the landscape. After one particularly deadly conflict at Crystalmaw Pass, both sides of the war were hesitant to return to the battlefield. With the soldiers gone, several local groups have moved in to fill the void: on the Plane of Earth, an enterprising bandit group called Sundered Stone claimed the space as their base of operations while earth creatures like xorns returned to the region.