Silver Horn of Valhalla

You can use an action to blow this horn.
In response, 2d4+2 warrior spirits from Valhalla appear within 60 ft of you. They
use the statistics of a berserker.
They return to Valhalla after 1 hour or
when they drop to 0 HP.
Once you use the horn, it can't be used
again until 7 days have passed.