The berserker would live blissfully at the hall of slain warriors, which is a palace roofed with shield’s called Valhalla, under the leadership of god Odin. The berserkers would feast on the flesh of a boar slaughtered daily. They would drink liquor that flowed from the udders of a goat, and their sport was to fight with each other every day, training for the ultimate combat, the fight against the giants.
The English word berserk is derived from the Old Norse words ber-serkr meaning a "bear-shirt" i.e., a wild warrior or champion of the Viking age,
Berserkers (or "berserks") were champion Norse warriors a wild warrior or champion of the Viking age used during the Icelandic sagas and would fight in a trance-like fury, a characteristic which led to the English word "berserk."
During battle, the berserkers would go into fits of frenzy. They would howl like wild beasts, foamed at the mouth, and chewed the iron rim of their shields. They were strong as bears or wild oxen, and killed people with a single blow.
During these fits they were immune to steel and fire, which would cause havoc in the ranks of the enemy. It is believed that berserkers could blunt their enemy's blades with spells or a glance from their evil eyes. When the rage abated they were weak and tame.
To "go berserk" would be to "hamask", this translates to "change form", "entering into a state of wild fury". Some have interpreted those who could transform as a berserker was typically as "hamrammr" or "shapestrong"; literally able to change shape into a bear's form.
Scandinavian kings would use berserkers as part of their army of hirdmen and sometimes ranked them as equivalent to a royal bodyguard.
The rage a berserker would experience was referred to as berserkergang or "going berserk".
This occurred not only in the heat of battle, but also during laborious work. Men would perform things which otherwise seemed impossible for humans. Going berserk would begin with the body shivering, chattering of the teeth, and a chill throughout the body, then the face would swell and change colour. Then at last gave over into a great rage, under which they would howl like a wild animals, attacking anything in front of them without discriminating between friend or foe. When this condition ceased, they would suffer a great dulling of the mind and feebleness, which could last for several days.
When Viking villages went to war in unison, the berserkers often needed to ware special clothing, such as furs from a wolf or bear, to indicate that this person was a berserker, which would warn others that he would not be able to distinguish friend from foe when in a rage, other allies would know to keep their distance.
Psychiatrists today have made explicit connections between the berserker rage of our soldiers at war and the hyperarousal of post-traumatic stress disorder.
Psychiatrist working with Vietnam veterans have stated the following:
“If a soldier survives the berserk state, it imparts emotional deadness and vulnerability to explosive rage to his psychology and permanent hyperarousal to his physiology — hallmarks of post-traumatic stress disorder in combat veterans. My clinical experience with Vietnam combat veterans prompts me to place the berserk state at the heart of their most severe psychological and psychophysiological injuries”