I've spent quite some time working out how to expand my Genestealer Cult so that I could use more of the rules from the Tyranid codex via proxies. It's a hard line to tread because using full on Tyranids with Imperial Guard would be just plain silly and narratively wonky beyond acceptability. It just wasn't going to happen.
For what seems like days I've been 'meditating' on the idea, looking at available models, thinking about the fluff, annoying my brother with endless 'what if...' messages, and going back to the Rouge Trader book for inspiration. It was then that I realised the answer was staring me in the face the whole time. Zoats. Zoats have a really interesting place in the early background of the Tyranids. Back at the beginning, Tyranids were smallish aliens who bioengineered creatures to do their bidding and fight in their hive fleet armies. The Zoats were the most intelligent of these creatures and were even used in diplomatic missions ahead of a hive fleet to see what kinds of civilisations lay ahead and to estimate the level of resistance the vanguard would meet. Some Zoats rebelled and fled to set up as independent forces in their own right.
All this comes before the Tyranids simply became this relentless meat-barrage of the hive mind. Contempory Tyranids - aside from a couple of special characters - have lost all the interesting narrative promise that they had in the early days. It's a pity because the idea of a highly alien race creating bioengineered creatures to do their bidding and fight their battles is very appealing - much better than the 'bio-Borg' antics of current 'Nids.
Enter the Zoats as I see them. Originally created by the Tyranids, many escaped their rule when they realised they would just be absorbed back into the hive both organically and mentally. This was not the fate they aspired to, so they fled to set up their own colonies, as far away from the Tyranid menence as they could manage. They took with them much of the bioengineering knowledge that the early Tyranids had depended on and set about creating enhanced versions of their own kind - genetically enhanced Zoats - along with slave creatures designed specifically for servitude and war.
These Zoat colonies defend their own territories and act as mercenaries; they will take money, but prefer to take payment of more dubious kinds, sometimes slaves, other times masses of cadavers... basically anything that can be salvaged as bio-mass for the development of their slave-organisms and foot soldiers. So the Zoats are pretty bad news even if they sometimes prove to be useful allies.
I imagine that I will field the Zoats as an independent force although I also intend to use them alongside my Genestealer Cult. They will have struck up this deal with the Cult in an effort to secure some prime Tyranid genetic material with which to fine tune some particularly nasty monsters for the battlefield. The Genestealers distance from the hive mind will give the Zoats some confidence that they won't be find out. Although whether this confidence is misguided remains to be seen...
With the basic background in place, I'll explain how I'm planning on modelling the army in my next post.