How to breed a passive set
Passives are inherited from the parents' combined pool, so the whole game is about controlling that pool. The community-proven method:
The core principle
A child can inherit up to four passives from the combined set of both parents. If the two parents together carry exactly the four passives you want and nothing else, every inherited passive is one you want. Splits of 4+0, 3+1, or 2+2 across the parents are all equivalent — what matters is the combined pool has no junk.
Step by step
1. Gather the four target passives onto two parents between them, with as few extras as possible.
2. Strip junk. A parent carrying a fifth, unwanted passive can pass it on — breed those out first by pairing with a clean mate and keeping children that dropped it.
3. Use a Special Cake when going for the full set — it raises the chance of inheriting multiple passives at once.
4. Repeat. Passive inheritance is probabilistic; expect several eggs. Volume beats luck.
Passing down special passives
Mutation-only passives (Immortality, Idiosyncratic, Babysitter, Heavily Armored, Skymarcher) and World Tree passives, once on a Pal, breed down like any other — so you only need to obtain them once, then fold them into your pipeline. 1.0's Pal Surgery Table and Disposable Implants also let you add some passives without breeding.
This is the practical summary. For the underlying breeding-power mechanics (how the
species is decided), see the
Vanilla Breeding Wiki, and use the
Cake Room to find the parent pairs that make your target species.