Why is Ren tortured by the Keepers in the novel, Wolfsbane?

Ren was to be Calla's mate and to lead the Nightshade pack with her. However, on the night of their union ceremony, Calla learned that she was to kill Shay and she could not allow that to happen. As a result, Calla and Shay ran away and Ren was forced to lie for them. Ren has since been tortured by the Keepers and the other Guardian packs in order to give them information about Calla.