Gith

The history of the gith is rooted in a cruel twist of cosmic fate. Inspired by the great leaders for whom the race is named, the gith rose up to overthrow the mind flayers that held them in servitude. But after they won their freedom, two factions among the gith disagreed on what kind of civilization they would forge. That disagreement quickly flared into open hostility, and the two groups distanced themselves from one another to pursue their separate agendas. The githyanki were motivated by revenge and convinced they deserved to take what they wanted from the worlds they travel to. At the same time, they hunt down and kill mind flayers whenever possible, as recompense for what the illithids did to them.
The githzerai believed that the path to an enlightened civilization lay in seclusion, not conflict. Their dedication to the principles of order is so strong that they can manipulate the stuff of chaos and use it to their benefit, and have carved out a stronghold for themselves on the plane of Limbo. Though the githzerai tend towards pacifism, they share the githyanki’s hatred for mind flayers, and from time to time send out squads to destroy illithid outposts.
If the gith were to ever team up against the illithids, a combined force could conceivably tip the balance in their favor.
Githyanki
Once members of a people who escaped servitude to mind flayers, githyanki split from their cousins, githzerai, and fled to the Astral Plane. In that timeless, silvery realm, githyanki honed their psionic powers and built a great city called Tu’narath. They have since spread throughout the multiverse, starting in outposts outside the Astral Plane, called creches, where time passes and their children can reach adulthood.
A lanky people with skin tones of yellows, greens, and browns, githyanki complement their physical prowess with psionic might, instilled in them by mind flayers and cultivated over eons in the Astral Plane. Now all githyanki can use their psychic bond with that plane to access splinters of knowledge left behind by beings who travel, live, and die among the silver astral clouds. Githyanki who reside in the Astral Plane can live indefinitely.
Githzerai
Githzerai migrated to the Everchanging Chaos of Limbo after the ancient schism that split their ancestors from their cousins, githyanki. Limbo is a roiling maelstrom of matter and energy, collapsing and reforming without purpose or direction, until a creature exerts deliberate will to stabilize it. Through their potent psionic power, githzerai carved a home for themselves amid the chaos. As the ages passed, githzerai explorers ranged out to other planes and worlds of the multiverse.
Githzerai are generally slender, with speckled skin in shades of yellow, green, or brown. Eons of cultivating their mental powers within the endless chaos of Limbo have imbued githzerai with the ability to shape psionic energy to protect themselves and probe minds.