Horn of Valhalla

[ Cor du Valhalla ]

Wondrous item, rare (silver or brass), very rare (bronze), or legendary (iron)

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.
Four types of horn of Valhalla are known to exist, each made of a different metal. The horn's type determines how many berserkers answer its summons, as well as the requirement for its use. The DM chooses the horn's type or determines it randomly.
d100Horn TypeBerserkers
Summoned
Requirement
01-40Silver2d4 + 2None
41-75Brass3d4 + 3Proficiency with all simple weapons
76-90Bronze4d4 + 4Proficiency with all medium armor
91-00Iron5d4 + 5Proficiency with all martial weapons

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.
Dungeon MasterĀ“s Guide (SRD) D&D 5 › Magic Items