Gith

Formerly the intelligent Githerzerai and the strong Githyanki, there is now only the Gith. In the midst of mindflayer raids in the Underdark, the Githyanki made a pact with Lich Queen Vlaakith in order to escape into the Astral Plane. The cost of doing so was the complete genocide of the Githzerai- a cost happily paid. Under the rule of the Lich Queen, Gith society developed to be both militaristic and matriarchal. 
On top of this, they founded the city of Tu'Nareth, which became the realm's most prominent trading hub thanks to its location at the crossroads of the planes. People who live in this city don't age, resulting in centuries-old Gith despite their otherwise standard lifespan. Alongside their signature yellow skin and tall builds, the most distinguishing characteristic of the Gith is their beginner-level psionic ability. This trait can be honed over their lifetime and is either seen as a side effect of their home in the Astral Plane or as a result of their early interactions with the mindflayer colonies that used to hunt them.