The Formation and the Split of the Gith People

In its chaos Arren gave rise to the gith, a people who carried in their core the chaos and improbability of their progenitor. They knew not how to harness this quality, and as the sole inhabitants of Astalia's moons they had no neighbors to learn from, nor to share their own thoughts with. Serphala saw this isolated people and offered them guidance. He showed them order. The gith learned to find balance between this order and their natural chaos and grew into proud cultures. Some of the gith accepted a further option from Serphala and traveled down to the planet, where they lived among the other mortals. These gith honed their natural psionics into a prowess in divination, guided under their religious practices in the Handdara religion. Other gith remained on the moons, and they too developed their psionics, using them to variously enhance physical and mental abilities in their lonely cities.
In the year 3586 a terrestrial gith diviner was forced to answer a question xe had said was unanswerable. Xyr fellow diviners were all destroyed by the ritual, and xe gained omniscience. As a result, xe defied the Handdara faith and some gith followed to form the Yomesh cult. The two faiths grew further apart, and with them the cultures of the gith that practiced them. The Yomesh sought omniscience and trained their children in psionics. The Handdara, meanwhile, maintained their cultural emphasis on the connection between physical and mental meditation and training.
Though the Handdara githyanki and Yomesh githzerai grew further apart in their cultural values and the abilities they nurture in their children, the gith still share a common history, and the differences between them are learned, not inherent facets of their creation or biology.

Historical Basis

Some gith are known to still live on the moons. Their contact with the planet is exceedingly rare, but the occasional message, or messenger, will bridge the space between Astalia and her moons. Both githyanki and githzerai reside on the moons, and communities and lunar gith families often include both variations, as the form psionic abilities take is shaped by the training an individual chooses to undergo.
The planetary gith include both githyanki and githzerai as well, though the two groups tend to align closely with the Handdara and Yomesh religions, and as such the two cultures keep themselves more separate and defined. Like their lunar relatives, the form of their psionics is determined by their training, but those gith born into one group rarely, if ever, access the other culture's training.