From Warhammer - The Old World - Lexicanum
|There's a legend that the Skaven are all descended from Skavor, the son of Gazul, cousin to Grimnir. Skavor, like Gazul, was younger than his brothers and lacked the skill for working stone or shaping metal. He was rightly exiled for this, so he went away into the deep-earth and learnt how to shape his flesh instead of shaping metal turning himself into a hideous rat-beast and swearing venegance on his blood-kin. And this is why the Dwarfs fight the Skaven as hard as we fight the Greenskins, though the Ratmen have wreaked far less damage upon us: because many of us believe that the Skaven come from our blood. We fight them not just to settle our grudges, but to shed our shame.