Two nations rule this world, both human (there are no non-humans here), in a constant state of cold war. The Malikid Sultanate and the Latifid Emirate are more alike than they are different. Both have absolute sexual equality. Both frown on sex outside of marriage, but both polygamy and gay marriage are perfectly accepted. In both civilizations, all people wear tagelmusts when not in private dwellings.
The people of the Malikid Sultanate, ruled from the capital of Kemmet by Sultan Malik X, worship the hippopotamus goddess Tem-Et-Nu. Their uniforms are purple, and their weapons are bronze.
In the Latifid Emirate, ruled from Qarya by Emira Duqa IV, worships the sun god Aurifar, and their uniforms are orange. They have a slight edge in the war, for their weapons are iron.
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Countless centuries ago, before the desert came, there were two civilizations, also at war with one another. But one of these civilizations devised a terrible superweapon, a scroll of great power, which scoured the world of their foes, but also made the world unbearably hot and dry, crumbling the civilization into dust.
After the war's end, two factions arose: one which thought the scroll was too dangerous to ever be used again, and wanted it destroyed; and the other, which thought the scroll should be held in reserve in case some terrible threat should appear.
As a compromise, the scroll was torn in two. Half of it was destroyed, the other half stored in a tomb protected by many traps and curses. The scroll is unusable in this state, but a team of science-mages could potentially reverse-engineer the rest, given years of study.
Centuries later, these two factions are now known as the Latifid Emirate and the Malikid Sultanate.
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My players, although initially on a mission to retrieve the weapon for Sultan Malik, decided in the end to destroy it so neither side could recreate it and use it, effectively siding with the Latifids. (The detail that the two factions of the ruined civilization eventually became the two modern nations was one that the players filled in themselves: it hadn't occurred to me, but it made so much sense that I ran with it.)