Sisters of the Coda
Around 1800 BCE, a Kheran colony ship laden with botanical goods was attacked by Daemonites over Earth. The Kherans ejected at the last minute, but the escape pods spread them across the earth and separated them from their wrecked vessel. The immortal Kherans were separated from one another by continents and oceans alike, scattered to the winds, while the remains of their colony ship crashed into an ancient caldera in Africa.
The Daemonite forces fared little better, crashing into the earth below. Weakened and isolated, the Daemonites and Kherans entered another state of detente in their endless war. The Daemonites found humanity to be effective and convenient hosts, and over the millennia frequently attempted to subvert entire civilizations.
The women of Khera discovered among all humanity allies who understood ancient and endless enmity. The Amazons of Bana-Mighdall were discovered not long after the founding of that city and strong relationships were immediately forged. The Kherans were welcomed there, over time-- men and women alike, a rare exception for males among the Amazons. The immortal Kherans taught the Bana-Mighdall much of war, of advanced weapons and metallurgy and science.
It was from the rare mating of Kheran and Amazon that the first half-breeds were born. The female Kherans, unable to procreate readily themselves, dedicated their lives to defending these new Kheran children and protecting Bana-Mighdall. They came to call themselves the Sisters of the Coda.