To coincide with the release of Mordenkainen’s Tome of Foes, the Adventurers League will be offer an all-gith module called “Rrakkma.” Chris Lindsay explains that it introduces the two gith races as AL legal by making them part of the Sha’sal Khou, an organization of githyanki and githzerai aiming to reunite their races (so players can have PCs of either race in AL games and not want to attack each other, handy that). The advenutre will have pre-generated characters – half githyanki, and half githzerai.
For those newer to D&D, the two gith races – githzerai and githyanki – were a single race enslaved by the mind flayers millenia ago that fought for their freedom, greatly weakening the mind flayer galactic empire, but then turning against each other. Githzerai would form rrakkma parties to go on mind flayer hunts. So this adventure focuses on that aspect.
I will have to dig around and see when it was really first introduced, but the first reference I could find to the Sha’sal Khou is in the “Lich Queen’s Beloved” adventure in Dungeon #100 which was part of the “Incursion” articles cross-over between Dragon and Dungeon magazines (and Polyhedron, too, I believe). Dragon #309 discussed running a campaign where the githyanki mount a massive invasion of the world. Dungeon magazine had a high level adventure where the PCs take on the Lich Queen of the githyanki (Vlaakith CLVII) herself. If I recall, Polyhderon (the official magazine of the RPGA at the time, and the backside of Dungeon magazine) had one of their “mini games”, in this case a D&D campaign idea where the PCs play the invading githyanki. The Sha’sal Khou were also included in the 4e adventure path “Scales of War” although I’m unfortunately less familiar with that and need to read up on it more.
It is looking like they are definitely leaning heavily into the planar side of Mordenkainen’s Tome of Foes!