Astrid Bjornrittar, in Brunnhildar Village, wants you to use the Reins of the Warbear Matriarch inside the Pit of the Fang and defeat 6 Hyldsmeet Warbears.
Besting a tethered opponent is one thing. Fighting other bear riders on equal footing is another.
Head into the Pit of the Fang and use what you've learned to defeat your opponents. Good luck, sister.
Glory awaits, should you succeed.