nova’s notes

(Side note: There’s a whole ongoing discussion on how the terminology was changed in 5E from “races” of humanoids to “species” of humanoids that’s tangentially related here with many insisting that calling the different types of humanoids different species implies they can’t interbreed and produce fertile offspring (which is not a universal rule even in our own reality), but I digress.)

During the time of their enslavement, their bodies had to adapt to living in the Astral Plane and in addition to this, were heavily experimented on by the mind flayers. It’s not exactly known if the egg laying and sterility of non-egg-layers is a “natural” by-product of living in the Astral or if it’s the result of the experimentation, but it is only a more “recent” change. The Githyanki are still humanoid mammals who just happen to lay eggs now. If it helps, you can equate them to a platypus, which both lays eggs and produces milk to feed its young.

In addition to laying eggs, Githyanki also have more highly developed psychic abilities and “atrophied” digestive systems. They require extremely frequent meals of very high protein foods to live outside of the Astral Plane. I put “atrophied” in quotes because I think high protein foods might actually be more difficult for a person with an atrophied digestive system to digest, but that’s how the lore books describe it.