The Ever-Changing Chaos of Limbo was an Outer plane that embodied the chaotic neutral alignment. It was the home of the Gith for millenia before it fell to the Illithids in an even known as the Spellplague. After that, the entire plane was lost to ruin, forcing the Gith the flee to the Underdark. Menyar-Ag was able to seal himself off from the devastation, choosing to stay in Limbo, locked away from the rest of the Outer Planes. Still he is able to guide and protect his followers, though from the lost plane, his powers are greatly diminished.
Many of the Gith were captured and enslaved by the illithids during this time, and those taken became known as the githyaki. The rest of the survivors, under the guidance of Menyar-Ag, aligned themselves with the Arcadians, and became known as the githzerai. They serve as psionic warriors in the Unknown, defending Arcadia from the scourge of the illithids.