"humans on fire came shrieking forth like berserkers"

Norse bronze plate depicting bersekers
Public DomainNorse bronze plate depicting bersekers - Credit: Oscar Montelius

Berserkers were ferocious Norse warriors who fought in a nearly uncontrollable trance-like fury.

A number of theories have been offered as to what caused berserker behaviour. Some historians believe the warriors worked themselves into a rage through some psychological process, while others claim drugged foods, such as hallucinogenic mushrooms, may have been ingested. Others suggest the beserkers may have suffered from some form of mental illness or handicap.