
There is an ongoing “eggs” and “hatching” theme throughout the Twisted Wonderland game, manga and novel that seems to be hinting at something that has yet to be fully revealed or explained.
While “egg of something” is typically just a form of expression in Japanese the game’s creator, Toboso Yana, might be interpreting it literally for wordplay:

Starting with the prologue of the game (and manga and novel), there is an explanation by Crowley that the school is an institution for the “eggs” of magic users from all over the world.

This is explained in more detail in Book 5 by Rook, who tells Deuce, “You are but a chick still inside your egg…ensnared as you are in the throes of hatching, each of you has an egg tooth that no one else possesses.”

Rook uses this “egg tooth” as a metaphor for unique magic, which Deuce discovers after once again being referred to as the “egg” of a magic user.

This is certainly one interpretation: the students enroll as eggs, and hatch into mages with the discovery of their unique magics. But not all unique magics are discovered at the school, with Riddle learning his by the age of 10.

And eggs come up often throughout the story, not only in reference to unique magics:

・Grim gets into a fight with students after breaking the yolk of someone’s carbonara
・Deuce gets a carton of eggs broken by bullies
・An unknown student contributes to Riddle’s overblot by throwing an egg

・Like Crowley, Trein also refers to the students as unhatched eggs of magic users
・An unnamed character during Glorious Masquerade also refers to the students as the eggs of magic users

・Egg sandwiches in the cafeteria
・Malleus was hatched from an egg

Yana has referenced the egg motifs, commenting in 2022 on the coincidence of an egg-based Master Chef event running at the same time as the Heartslabyul novel was published along with the chapter of the manga where Riddle is struck in the head with an egg.

While the three forms forms of media being released simultaneously may have been a coincidence, the consistent egg themes seem intentional 🥚