We know that Githyanki hatch from eggs from this question.
Is there a specific source that says the Githzerai hatch from/lay eggs?
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Sign up to join this communityWe know that Githyanki hatch from eggs from this question.
Is there a specific source that says the Githzerai hatch from/lay eggs?
Mordenkainen's Tome of Foes details that the Githyanki and Githzerai are simply two factions of being a Gith:
But after they won their freedom, two factions among the gith disagreed on what kind of civilization they would forge.
The factions are mechanically described as sub-races of Gith, not as separate races. The descriptions begin with the standard Gith, and then provide the specifics for the Githyanki and Githzerai. This similar to the primary heading of Dwarf and then choosing Mountain Dwarf or Hill Dwarf. Many races have subraces (halflings, elves, etc.).
With this in mind, the linked question you begin with on whether Githzerai lay eggs remains the answer to this one: They do (MM, 87).
Githyanki hatch from eggs.
But after they won their freedom, two factions among the gith disagreed on what kind of civilization they would forge.
These factions are later described as the Githyanki and the Githzerai.
Further, MToF lists the two as subraces of Gith. No matter which you choose to play, the race details state, "Your character shares the following traits with other gith", then goes on to detail the specifics of each subrace.
The confusion is understandable, twice in MToF the two are referred to as "two races", but I do not see any reason to believe that the Githyanki and Githzerai are different races in such a way that their biology would be so fundamentally different that one would lay eggs and one would not.
It is unknown. I fall on the side of no, 'zerai do not lay eggs. First it is never specifically mentioned that all gith do, nor that 'zerai do, only that githyanki do. That is telling in and of itself. Secondly, it is clearly stated that yanki must hatch their eggs outside of the Astral plane, as time doesn't exist there. They have specific areas to do this across the planes. No such life cycle is mentioned for the zerai. My conclusion, while it is possible that they both lay eggs, I think only the yanki do. For while they are 2 branches of the same race, their time in different planes has altered them (stated many times), resulting in the yanki evolving an egg laying life cycle. Some people say it's because of their link to red dragons too, idk, just my 2 cents.
References: Mordenkainens tome of foes, forgotten realms wiki