Qifrey obviously has a personal reason to track down the brims. Maybe one of them killed his wife, or something. He's not going to let the fascist Council or anyone else get in the way of his revenge. Alternatively he's seeking some blasphemous spell to use for his own purposes, but I reckon people would know about it if he had such a motive, and he would be observed all the time, so I don't consider this option as likely.