Magical gene / ground and strong white

Imperial

A white cape starting at the withers and working forward up the neck - reaching the poll at full coverage - with slivers of coat left showing between its branches. A third allele carries the same marking worked in greys instead of white - dark where the pale form is light, and the same number of steps.

What it can come out as

Outcome	Carrying
Imperial	`Sbi/Sbi` · `Sbi/Sbc` · `Sbi/n` · `Sbi/Sbk`
Black Imperial	`Sbk/Sbk` · `Sbk/Sbc` · `Sbk/n`
Coloured Imperial	`Sbc/Sbc`
Wild type	`Sbc/n` · `n/n`

How each one is actually drawn - region by region, and the layers it is built from - is on the coding tab.

Crossing two of them

Finding one

About 1 in 893 wild horses is born showing this. That is the whole of the supply: catch one, or make one with the carrot below. Breeds set their own pools and a breed built around this gene will carry it far more often than the wild population does.

Wild pair	Shows as	How often
`Sbi/Sbi`	Imperial	0.004% — 1 in 25,000
`Sbi/Sbk`	Imperial	0.0053% — 1 in 18,751
`Sbi/Sbc`	Imperial	0.0053% — 1 in 18,751
`Sbi/n`	Imperial	0.076% — 1 in 1,316
`Sbk/Sbk`	Black Imperial	0.0053% — 1 in 18,751
`Sbk/Sbc`	Black Imperial	0.0053% — 1 in 18,751
`Sbk/n`	Black Imperial	0.0053% — 1 in 18,751
`Sbc/Sbc`	Coloured Imperial	0.0053% — 1 in 18,751
`n/n`	Wild type	99.888%

Its gene carrot

The file

common/src/main/resources/horsegenetics/genes/imperial.json — a data-driven gene, not a Java class. It is listed in the index.json beside it and registered by Genes' class initialiser at startup.

Key	`horsegenetics.imperial`
Phase	magical — it adds signed colour in phase 3, after the pigment has resolved
Priority	206 — where it sits in the one `(priority, key)` paint order
Alleles	`Sbi` · `Sbk` · `Sbc` · `n`
Varies per horse	3 values drawn once off the expressing allele copy, so a foal that inherits the copy inherits the look
Built from	AXIS, PARTS, STROKES, TOWARD

Why it is built this way

The black allele is the white one with the light taken out of it, and it sits one rung under white in the dominance series - so every combination that existed before it keeps the outcome it had, and only the pairs carrying Sbk are new. The re-toning is a mapping rather than a repaint: every achromatic target moves into the dark end of the scale keeping its order and its spacing, and every SATURATED one is left alone, because that colour is the gene rather than its lightness.

What it paints

Each outcome, described the way the gene file describes it, and then the layers that draw it in the order they are painted. The prose is the part a reader checks a bake against; the list underneath is what the engine actually did.

Imperial

A cape or blanket shape: it originates at the withers and extends up and forward, broad across the neck and shoulder and running as far as the poll when the coverage is maximal. Its edges are defined but irregular, and it is never solid - slivers of the coat beneath must show through between the branches, and a horse whose neck is simply white is not an Imperial. The branches always join up somewhere: a full wrap around the neck on a heavily marked horse, or a narrower connection dipping into the chest and under the elbow on a lightly marked one. It only ever expresses as white, which is what separates it from brindle and every other stripe-adjacent marking.

the cape over the withers and up the neck — PARTS × AXIS × AXIS × STROKES inverted, painted with TOWARD

Black Imperial

The same marking as the white form with the light taken out of it: a single near-black tone.

the cape over the withers and up the neck — PARTS × AXIS × AXIS × STROKES inverted, painted with TOWARD

Coloured Imperial

The same cape in a colour the line carries rather than in white - which the marking's own tradition says is not an Imperial at all, but the genetics do not care. Fully recessive: it takes two copies, and a single copy beside the white allele shows white. It never gives blue eyes, whatever the white form does.

the cape over the withers and up the neck, in colour — PARTS × AXIS × AXIS × STROKES inverted, painted with TOWARD

Wild type

No cape.

Paints nothing.