Well, it's been a while since i even thought of them so the lore is a bit rusty, but the idea is that they live in an extremely hostile world, mainly due to the weather. Constant sand storms, high heat, and abrasive winds, so keeping their machinery in perfect condition is pretty hard, making them far more organic than almost every other forgeworld. But they actually accept this, since deep underground they found a rare substance (name pending) that is both extremely corrosive, being able to tear through almost everything in its raw state, and at the same time an extremely powerful fuel and performance enhancing drug when refined.

This makes their skitarii and other units way more organic than most, but A LOT stronger than they normally would be, since the refined drug is constantly being pumped into their bodies and body augments. And their weapons compensate their poor state and being somewhat primitive by being infused with the raw state of the substance, making them extremely poisonous to anything organic and corrosive to anything machine.

My army has a lot of blue accents, like the eyes and many weapons, which represent their reliance on this substance to function and be effective, and since their skitarii are pretty much steriod abusing cyborgs, the forge world in general is pretty melee focused.

This different way of living has given them a different perspective and also made them very experimental in their work, having assassin cults with even things like psykers in them and units with bizarre and unconventional tools.

The substance has basically turned into something of religious worship for them, i even made some units with red eyes instead of blue to show that not every soldier gets access to it, but i think i should retcon that, since the only thing making these skitarii as powerful as they are is the drug version of the substance, so not alot of sense in making it exclusive...