From the Ynglinga Saga:

“… his men went without mailcoats, and were as frantic as dogs or wolves; they bit their shields and were as strong as bears or boars; they slew men but neither fire nor iron could hurt them. This is known as ‘running berserk’.”

Nothing about any condiments here, but I prefer mine with wild mustard! The only thing more dangerous than an enraged berserker is a hungry one.