A famous-but-secretive order of women pulls the strings of all known civilization. They possess special powers, that allows them to do so, but even more than their powers they rely on their reputation and their vast network of connections. There is an important in-lore reason why the order accepts only women - the powers they use are defined by their gender, and the male version has some terrible aspects to it such that letting a man connect to it will be disastrous.

And yet - the order has a prophecy about a chosen one - a man that will use the power to unify humanity and lead it. For generations, the order's secret agenda was to track the bloodlines that will lead to his birth, all in order to ensure he is born under their control and guidance.

But as stories go - that doesn't work out. In the last generation, just before the chosen one is born, a member of the order betrays that goal. The chosen one is born outside the order's control (though not entirely outside its influence), and grows up training under a master swordsman.

We reach the first book. Boy leaves happily with his big happy community - which, of course, gets attacked and destroyed. Accompanied by a member of the order he manages to escape the massacre , and eventually reach the desert. There they meet up with the Bedouin themed desert nomads. These nomad are very isolated and xenophobic, but of course they eventually accept our protagonist. We learn a few things about them:

While they are known through the world as fearsome warriors, in their past they were pacifists.
Their women can also use the same power the order uses. They just... use it for their own tribe's businesses instead of interfering with governments.
They also have a prophecy about a chosen one that would lead them. And surprise surprise - it's the same chosen one the order was going for. What are the odds?

Well, chosen one or not - there is a tradition to be held. So our protagonist goes through their tests, becomes their great chieftain, takes a chieftain's daughter as his lover (which won't stop him from marrying a more conventional princess), and goes on to use them to do his chosen one business and take over the entire civilization.