Xipoli Continent Elven Law Volume 31. When humans exchange their eggs, there is inevitable wear and tear involved. As everyone's spiritual strength differs, the amounts of damage each egg could withstand differs as well.
2. After the egg suffers sufficient damage, it will disappear, and the owner of the egg will forever become a woman, and never be able to revert. The continent calls these people "Eggless".
3. After the exchange of the eggs, both parties will receive the "Elf's Blessing". Apart from the clothes mentioned in the first volume, the more important benefit is that only through this do the two gain the ability to reproduce.
4. "Eggless" are unable to be a part of proper marriages, and also never receive the ability to reproduce.(Addendum): Naturally born "Eggless" do not exist.