The name for the fit a berserker
suffered when making the transformation from human to killing machine.
Contrary to popular belief, this transition, which allowed the individual so stricken to perform deeds of superhuman strength and ferocity did not only occur in the heat of battle but also during peaceful labours, and an account exists of a father being overcome with the berserk rage while playing ball with his son, who was only spared by the intervention of a servant woman (who paid with her life before the rage faded.)
Sources document the berserkergang manifesting first as a chill in the body, accompanied by chattering of the teeth and shivering. This stage of coolth surpassed, the face swelled and changed its color, engorged with blood and announcing a great hot-headedness, eventually climaxing as a great rage in the throes of which they would howl as wild animals, bite the edge of their shields and indiscriminately cut down everything they met, friend or foe alike.
When the condition passed, a great dulling of the mind and feebleness was reported to have followed, lasting for an indeterminate period from one to several days.