Genetically engineering lifted psychic powers above the random background of coincidence. Backlash and prejudice against 'magic' and 'satanism' resulted in the exile of the genetically engineered to dangerous worlds, not-quite-parallel earths they weren't expected to survive.
Thirteen centuries of turbulent Earth history later the exiled magicians have been forgotten, rediscovered, clashed with . . .
The Empire of the One grew from the accidental stranding of an early exploration party of the genetically engineered, two years before the Exile. They arrived in the middle of a war, where the three great powers, China, the Islamic Union, and Greater Argentina vied for possession of the ruins of Europe and North America. The marooned explorers used their special talents, and a lot of flimflam and fast talk to place themselves on the top of the Islamic Union as the New Prophets of the One True God.
Fourteen hundred years later, their descendants are still the elite of a united world with eleven cross-dimensional colonies.
And their kids still have to go to school.