Put two Pals and a Cake in a Breeding Farm and the egg you get is not random. Every Pal carries a number the game never shows you, called CombiRank in the data. The child is worked out from both parents' ranks, and the whole system is one formula plus one override table.
The formula averages the parents
The game first works out a target:
target = ceil( (parent A's rank + parent B's rank + 1) ÷ 2 )
It then looks through every Pal that is allowed to hatch from an average and picks the one whose rank sits closest to that target. Closest, not equal — most pairings produce a target that matches no Pal exactly.
Three worked examples, using the ranks in the site's data:
| Parents | Ranks | Target | Child |
|---|---|---|---|
| Lamball × Cattiva | 3050 / 2760 | 2906 | Daedream (2910) |
| Nitewing × Ribbuny | 2560 / 2860 | 2711 | Eikthyrdeer (2710) |
| Jetragon × Frostallion | 70 / 150 | 111 | Eidrolon Ignis (140) |
Lamball × 
Cattiva
Daedream (2910)
Nitewing × 
Ribbuny
Eikthyrdeer (2710)
Jetragon × 
Frostallion
Eidrolon Ignis (140)The third row looks wrong at first. The target of 111 is one point away from Frostallion Noct (110), yet the egg is an Eidrolon Ignis 29 points further off. Frostallion Noct simply is not in the pool.
About tied distances
There is a tie-break rule in the algorithm: if the target sits the same distance from two Pals, the higher rank wins.
You will never see it fire. Every one of the 299 ranks in the current data is a multiple of 10, and the target always ends in 1 or 6, so its distance to any Pal ends in 1, 4, 6 or 9. Two distances can never come out equal. The rule is insurance against a future rebalance.
75 Pals the formula can never produce
All 299 Pals have a rank, but only 224 are eligible to be the child. The other 75 sit outside the pool:
- The five legendaries and the nine tower bosses: Jetragon, Frostallion, Frostallion Noct, Necromus, Paladius
- Every elemental variant — Foxparks Cryst, Jolthog Cryst, Incineram Noct, Elphidran Aqua and the rest
- The Terraria collaboration Pals: Eye of Cthulhu, Enchanted Sword, the slimes
Frostallion Noct, 
Necromus, 
PaladiusThey breed perfectly well. They just cannot be averaged into, which means the override table is the only way to get one.
The override table wins
The game ships a fixed pairing table, 258 rules in the official data. If your two parents appear in it, the formula is skipped entirely and the table decides. Everything in the list above depends on it.
| Parent | Parent | Child |
|---|---|---|
| Relaxaurus | Sparkit | Relaxaurus Lux |
| Frostallion | Helzephyr | Frostallion Noct |
Relaxaurus
Sparkit
Relaxaurus Lux
HelzephyrA large block of the table is just "same species × same species = same species". Those entries matter most for the Pals outside the pool: without them, two legendaries would hatch something unrelated.
The official table has a parent-gender column, and a few pairings produce different children depending on which parent is female. The site has no gender model, so it reports the female-parent result.
Using it in practice
Working the formula by hand is for understanding it. When you actually want an egg, the breeding calculator takes two Pals and gives you the child, or works backwards from a Pal to every pair that makes it. The breeding path finder takes the Pals you already own plus a target and returns the chain that hatches the fewest eggs.
Two things trip people up.
Rank has nothing to do with strength. It is a sort key. The lowest in the pool is Aegidron at 30, the highest is Teafant at 3070. Getting a strong low-rank Pal usually means pairing two low-rank parents, not two strong ones.
Teafant at 3070. Getting a strong low-rank Pal usually means pairing two low-rank parents, not two strong ones.Every egg costs one Cake: 5 Flour, 8 Red Berries, 7 Milk, 8 Eggs, 2 Honey. What throttles a breeding operation is nearly always wheat and ranch output rather than the pairings themselves.
The ranks, the pool and the override table all come from the site's current game-data snapshot, the same one behind the breeding calculator.