You have dedicated your pain to the service of your god, and regular and repeated self-inflicted wounds mean that pain now only incites you to greater feats. You feel no pain and may ignore penalties inflicted by Critical Wounds, other than amputations.
Additionally, if another ability or effect allows you to Frenzy (page 184), you may enter a Frenzy any time you suffer a Wound without requiring a Test.

Core Book, Page 119