Flayerkin are twisted Chaos Marauders who have replaced their hands with wickedly sharp hooks and claws. These claws serve a dual purpose: First, they are extremely effective weapons, as they are an extension of the Marauder’s arms. Second, they allow the Flayerkin to gain purchase on nearly any vertical surface.
In addition to their modified limbs, Flayerkin are draped in ropes and chains that they use to help their brethren in the scaling of sheer surfaces, such as keep walls. Even a dead Flayerkin can be used as a sort of organic siege ladder for the other members of his warband, and indeed were in the Storm of Chaos.