Kate Argent, newly transformed as a nagual, acquired two Berserkers. They naturally came to serve her, helped her survive, did her bidding. She used them as bodyguards and man power. Kate could issue direct commands to them by roaring. When a berserker was about to kill Chris Argent, she gave out a roar and the demon spared her brother's life.
Kate used a captive Scott McCall as a human vessel for a new Berserker. She did this by the following ritual: she outfitted Scott with an animal bear's skull, while apparently falling into a trance. Scott then underwent a transformation, the Animal spirit of the demon being summoned, possessing Scott, taking over the personality of its human vessel. Afterwards, Scott was completely submissive and loyal to Kate, following her order to attack and attempt to kill his friends.