Horn of Valhalla, silver or brass

You can use an action to blow this horn. In response, warrior spirits from the Valhalla appear within 60 feet of you. They use the statistics of a berserker. They return to Valhalla 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  Silver horn summons 2d4 + 2 berserkers and has no requirement. The Brass horn summons 3d4 + 3 berserkers and requires proficiency with all simple weapons. The GM chooses the horn's type or determines it randomly.

If you blow the horn without meeting its requirement, the summoned berserkers attack you. If you meet the requirement, they are friendly to you and your companions and follow your commands.