Clan Skaul

It isn’t entirely clear to anyone why Clan Skaul maintains its position on the Council of Thirteen. The clan’s population is composed almost entirely of hedonists and addicts who persist in making extensive use of Warp-laced narcotics. One answer for their success may lie in the fact that several Grey Seers have been born to Skaul’s breeders within the past five decades. Some postulate that the drug use of the clan’s rank and file may have something to do with the increased number of Grey Seers being born there.

Source

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