Concerning “half-breeds”

[Kaede45]

So I’ve been thinking about how I’m trying to make a sort of cosmopolitan faction, where Humans & Xenos live together & the thought came up about inter-species relations. I know the Imperium is so xenophobic that even the thought is likely considered heretical & the closest we have to a cosmopolitan empire in cannon is the T’au, but they seem to practice segregation to a degree, but I’m sure I’ve heard of at least one half-breed. I believe it was a half-Human, half-Aeldari who was a clone made by either Malcador or Cawl, but I’ve been thinking ”what about other types of half-breeds?” I know that the GSC are also technically half-breeds, but I don’t really count them. I’m talking “mom was X & dad was Y” type half-breeds. How would they function? Would they take more after one species or the other? Are they any different from either of their parents?

 

Additionally, I know that the T’au are divided into different castes & the Ethereals regulate who they can & cannot mate with, but if they could freely interbreed, what would the children of two different castes look like? Would they create an entirely new caste or would they simply be born of one caste or the other? Would the children of a fire caste T’au & a water caste T’au be a “steam” caste or would they simply produce children of either water or fire castes? Would any caste’s genetics be dominant or recessive when compared to any other?

 

Also, what about half-Abhumans? Would they create new Abhumans or be more like one of their parents? Would the Human gene be dominant over the Abhuman gene, thus their children would not be Abhumans at all? Do an Ogryn & a Ratling produce something in the middle or one or the other or would they simply produce a Human?

 

Finally, how would these half-breeds translate to the tabletop?

 

These are just the theories I’d like to explore with this topic. Feel free to chime in with your own theories or answers to these & other questions. As always, thank you very much for your time & of course, God bless.

[Karhedron]

From a biological point of view, half-breeds should be impossible. We are not genetically compatible with chimpanzees despite being close in evolutionary terms and sharing 98% of our genomes. Genestealers get a pass because they are designed to infiltrate other species but anyone else should be pretty much impossible. After all, all life on earth is based on the same 4 letters of DNA. Alien species would likely have an entirely different genetic alphabet.

 

Mixed abhumans might be possible as they are mostly human. You could probably get a ratling/ogryn cross in the same way that a you can cross an Alsatian with a Terrier. The concept of dominant genes only really applies to single trait mutations like eye colour. Humans have 20,000-ish genes so it probably takes hundreds of mutations to produce an abhuman. It is very unlikely that a cross between 2 abhumans would result in a pure human. Imagine have 2 Labradoodles and trying to get pure Labrador or Poodles as puppies. It might be possible in theory but in practice you would have better chances of winning the lottery. Mixed abhumans would probably have a mix of traits from their parents.

 

The only way mixed human/alien hybrids might exist would be with outside assistance/interference such as the case of Ael Wyntor. 

[Dr. Clock]

1 hour ago, Karhedron said:

Alien species would likely have an entirely different genetic alphabet.

I real life I'd agree, but as soon as we allow that the 'alien love gardeners' the Old Ones were going around in antiquity seeding the galaxy with lots of life, there is no reason to assume that they wouldn't have set up the capacity for hybridization whether by design or accident. That's to say that Orks, Humans, a Eldar at the least may come from the same 'original designs', and thus be 'blendable' in a way that 'natural evolution' wouldn't be. 

 

All that's to say that 'by magic or science' is how I'd approach cross-species hybridization in headcanon, as it is highly unlikely that gametes would be compatible across species in their conventional/natural state. 

 

Cheers,

 

The Good Doctor.

[N1SB]

There MIGHT be one, and I'm double-checking it.  You know him.  It's Typhus, or Typhon before the Heresy, of the Death Guard.

 

He carried the epithet/nickname of "the Half-breed", in fact iirc people back on Barbarus would call him that until Mortarion told them to stop.  Their home planet was ruled by this nobility referred to as the "Overlords", one of whom raised Mortarion.  Typhon was said to be the product of another Overlord and a human, his mother.

 

The difference was so stark that the human population killed his mother for consorting with an Overlord.

 

These Overlords were pretty inhuman, but I'm not 100% sure if they're xenos.  The best information we have on them is from The Buried Dagger 30k novel.  Barbarus was a toxic planet, the whole atmosphere was pretty poisonous, with only the lower altitudes survivable for humans and it only got more dangerous the higher you go.

 

The Overlords lived in ancient castles on mountaintops because they were immune, to show how different they were.

 

How bad was it?  Even Mortarion, the Primarch, couldn't survive for long up there.  He lived at the foothills in this like hut.  He had to design this special steampunk armour powered by his own arm and leg movements to pump this air filtration system.  And he famous for being one of the most resilient of the Primarchs.

 

But that in itself isn't definitive, and there are other possibilities to explain the above.  It's all ambiguous.

 

The book never quite explains what the Overlords are.  They could have been xenos native to Barbaros and conquered human settlers that had landed there.  Or Abhumans uniquely adapted to the planet...but why only them and not others?  Maybe a group that arrived millennia earlier, so had time to adapt?  Or so specifically genetically engineered to be immune to Barbarus's atmosphere.  It's possible an elite group of humans invented an airborne poison that they also made a cure for only themselves, then released that toxin onto the planet to subjugate the rest of the planet.  It's also pretty openly implied Barbarus was under the influence of Nurgle, so they could have been human cultists that made a daemonic pact for this immunity.  The Overlords had access to what seemed like magic or sorcery...but that might also be because they're strongly psychic xenos...from whom Typhon inherited the psychic abilities he was famous for in his infamously anti-psyker Legion.

 

Any of those possibilities, xenos, genetically modified (Ab)humans, Chaos cultists OR a combination of any of them could be true.

 

But Typhon, who was still a child when he met Mortarion, was believed to be a "half-breed", it was just accepted in the 30k era.

 

Edit - Checked The Buried Dagger earlier.  Mortarion's adoptive Overlord father was named Necare, and was described as "nightmarish and alien.  If his kind shared any kinship with humans, that history has been seared away and forgotten."  This is deliberately open-ended, but weirdly, re-reading those Barbarus passages, I kept thinking of Dark Eldar personally.  Just adding this as follow-through since I mentioned it.

Edited Thursday at 10:32 PM by N1SB

[Beef]

Well in 2nd edition they had half elder/Space marines and seeing as this is a fantasy game set in space anything is possible.

 

Its your hobby do as you want.  If your modelling for pleasure then it should not be an issue.  If your gaming you can have whatever back story you want as long as the models fit into whichever GW faction your playing.  Again unless your playing with friends etc

 

 

[jingus]

Maybe two xenos species could mix, like uhh the Necron consciousness goes into a Tau battlesuit. (I don't really know how Necrons work) 

[Kaede45]

2 hours ago, jingus said:

Maybe two xenos species could mix, like uhh the Necron consciousness goes into a Tau battlesuit. (I don't really know how Necrons work) 

Not sure how that would make a half-breed…

 

But speaking of the T’au, this is the second question thread I've made mentioning them where no one gave any answers concerning them. Are there so few T’au experts or do they all stick to their own little coven?

[N1SB]

On 8/19/2025 at 11:24 PM, Beef said:

Well in 2nd edition they had half elder/Space marines and seeing as this is a fantasy game set in space anything is possible.

 

This is a great point.  It was how they kinda weaved a retcon in there, which was very clever.

 

1st ed, an Index Astartes Ultramarine article, introducing Marneus Calgar, there was this half-Eldar Librarian of the Ultramarines, who was said to have come from the Dark Angels.  Like they could transfer between Chapters.  This was early stuff, I really should go back and look at that.  But his name was Illiyan Nastase, a memorable name.

 

(Illiyan Natase in the top right corner, he used to hold a book, too)

 

Recently, in the Dark Imperium and Dawn of Fire novels, the returned Primarch Roboute Guilliman introduces this Aeldari emissary sent by his old sometime ally, Eldrad Ulthran the Ulthwé Farseer.  Not a Librarian, not a Space Marine, just an Eldar psychic advisor.  He had a memorable name: Illiyanne Natase.

 

Strangely unlikeable despite being a diplomat.  Not really important in his own right, but shows Guilliman's style of leadership in a few key scenes.

 

Why was this interesting?  It shows the limits that GW set, like a marker that shows when something's too far.  There was no Half-Eldar Ultramarine, BUT there is an Aeldari psychic emissary in Guilliman's court.  Not a former Dark Angel, but wearing the dark robes of Ulthwé.  They heard the same name, but spelt different.

 

It's like in-universe, there were rumours of some Eldar serving the Ultramarines and the 1st ed article was simply misunderstood gossip.

 

This might help you in whatever project you're working on.  People in the Imperium call something a half-breed, but is it such?  Leave it open-ended.

 

When I was a kid, I spoke with Andy Chambers once, he was very nice and patient with me, but he told me what Rick Priestley told him, "Don't tie up loose ends."  It's supposed to be open ended.  You just have to imply.  But I'm still thinking if you want to do something crazy, it'd be an abandoned Dark Eldar slavebreeding experiment.

 

6 hours ago, jingus said:

Maybe two xenos species could mix, like uhh the Necron consciousness goes into a Tau battlesuit. (I don't really know how Necrons work) 

 

Indeed, Ork Genestealer Hybrids were a thing, I had a model, and "I don't really know how Necrons work" IS the correct answer.  NO ONE knows how Necrons work.

 

3 hours ago, Kaede45 said:

But speaking of the T’au, this is the second question thread I've made mentioning them where no one gave any answers concerning them. Are there so few T’au experts or do they all stick to their own little coven?

 

I dunno, I don't think so, but it's an interesting point to ponder.