Egg sizes and mutations
The official description ends by naming four things to chase: rarer eggs, anime, sizes and mutations. The last two are variants.
Sizes and mutations are variant layers on top of the base egg and anime. They are the reason two steals of the same target can be worth different amounts.
Two extra layers
Rarity answers the question "which egg is this". Size and mutation answer "which version of it did I get". The official description lists them separately from rarity, which tells you they are independent variables rather than synonyms.
Site panel: the size and mutation system, built from official game art.
Size
Size is a scale attribute. The game's own promotional art shows oversized eggs, and the description lists sizes as something you discover rather than something you buy. In practice a size variant is a second reason for a run to matter: the same target can produce a bigger, more notable result.
Mutations
Mutations are a modifier layered onto a hatch. Like sizes they are discovered, not purchased — no pass in the 31-item store is sold as a mutation item. That makes mutations the most luck-driven part of the collection.
What variants change for you
| Layer | Decided by | What it affects |
|---|---|---|
| Rarity | Which egg you stole | How special the entry is |
| Size | The specific egg instance | How notable the result looks |
| Mutation | The specific hatch | An extra modifier on the result |
Practical advice
Do not plan a session around a mutation. Plan a session around a route you can complete, and treat a size or mutation as upside. Players who chase variants before they can reliably finish a steal end up with a lot of failed runs and an empty plot.
FAQ
Are mutations guaranteed on any egg?
No source confirms a guaranteed mutation. The description lists them as something you discover, which is consistent with a chance-based system.
Can I upgrade the size of an anime I already hatched?
No. Size and mutation are set when the egg is hatched. The way to improve your odds is to run more successful steals.
Do size and mutation affect income?
Rarer and more notable results are the reason to keep running, but the description does not publish a number for variants. Treat them as collection value first.
