The Skaven are clearly not Recombinant, they are clearly a Chaos force of rat-beings from nowhere. And henceforth Vitchard Vox does not consider them true rats. The Skaven's Home Planet of Alga II is actually technically an indoor planet, but not as a Dyson Sphere, as all live underground. The Skaven number in the Trillions, and as such rival the Tyranids as such. They worship Slaanesh's biggest rival, the Great Horned Rat. And have tried to overrun Redwall at least twice, Cluny the Scourge is one such Skaven, but Vitchard, being a recombinant(made from Skaven parts at the very least), is allied with Metamor.