We currently have no concrete evidence to how the berserkers worked themselves up into such a frenzy, with mushrooms being just one of many theories. The myth that they used mushrooms comes from several places, one of its biggest factors being that other warriors from different cultures did use mushrooms (the Aztecs are one culture that did so I believe) before or during battle.

[–] r4venw@sh.itjust.works 2 points 1 year ago

I was under the impression that it was good old fashioned battle PTSD. Iirc, berserkers were reported to sometimes attack anyone nearby in their frenzy, not just the enemy faction.

[–] mudstickmcgee@sh.itjust.works 2 points 1 year ago* (last edited 1 year ago)

Another popular "theory" is that they would coat their shields in mushroom, ( either, fly agaric or liberty caps, depending on who you talk to) and bite them in battle to re-up their trip