Hello dice-geeks,
In order to "hatch an egg", you gotta play the
parallel universe from the character
robot. The following Wiki gives a few details about that special "egg":
https://diceydungeons.fandom.com/wiki/Precious_EggYou will need to find that equipment during the level and equip it. Than first roll a 6 and place it on the equipment. After that, it will require a 5, a 4, ...
When you will play the last one needed, a new equippement "hatches" out of the egg and the achievement pops right away for you.
The 6, 5, 4, 3, 2 and 1 can be placed on the equipment over the course of several battles, dont need to be in a single fight.
Here is also a video, owned by "Graytale" (I dont claim any right):