User blog comment:GSFB/Ulfhednar vs Werewolves/@comment-99.140.100.79-20120915140539/@comment-5232784-20120916011148

Yes, Ulfhednars were real, and so much like the Berserkers (who were just as powerful, but wore bear skins) that they were later absorbed in name into the Berserkers. No one knows for sure how they could become so strong and resistant to pain, but you can bet top money on the fact that adrenaline was involved, based on the symptoms of the warriors in question.

Berksers proper would get so mad with battle rage/fury that they would gnaw on their shields before battle. Ulfhednars would howl like wolves before a battle (and they had no shields).