You can use an action to blow this horn. In response, warrior spirits from the Valhalla of the plane of Ysgard appear within 60 feet of you. They use the statistics of a berserker. They return to Ysgard after 1 hour or when they drop to 0 hit points. Once you use the horn, it can't be used again until 7 days have passed. The iron horn summons 5d4 + 5 berserkers. The iron horn doesn't require proficiency.