Clan Skaar

Clan Skaar is known for its extensive mining operations. Skilled at ferreting out lodes of Warpstone, they often work closely with Clan Skryre and Clan Moulder, supplying each Clan with the precious substance. It’s rumoured that Clan Skaar plays a dangerous game, pitting Moulder and Skryre against each other. Most Skaven believe that this militarily weak Clan will eventually be destroyed, and their mining operations claimed, by Skryre, Moulder, or both.

Source

 * Warhammer Fantasy RPG 2nd ED -- Children of the Horned Rat pg. 50