Berserkers - or bear warriors - they were called, and in many ways they were the secret weapon of the Viking armies that conquered vast lands in the era where Scandinavian seafarers dominated the oceans and rivers of Europe. Berserkers were a special breed of extra huge and extra strong Viking warriors, and the most feared of all. In battle the berserkers would go totally ballistic, foaming at the mouth and howling like wild beasts. And when in this frenzy they were not merely strong, they were unstoppable. Some records even claim they were immune to swords or fire. Viking armies often put a contingent of berserkers at the front of their ranks, and the mere sight of these frothing beasts was often enough for the enemy to put down their weapons and flee. But who were these terrifying bear warriors, and what put them in this seemingly uncontrollable warrior mode? The answer is Hyoscyamus niger - more commonly known as Henbane. A rare herb, but very common in Scandinavia, especially on the once remote island of Sprogø. Today the island has no inhabitants, but back in the day it was known as The Island of Giants. Scientists have since found that the male islanders suffered from a genetic mutation, reducing their body fat and tripling their muscle mass. Combine big muscles with the hallucinogenic effect of Henbane - and you have the epitome of a warrior that was "strong as a bear and mad as a dog". These notorious Viking warriors are no more, and today you'd hardly notice their proud homeland as you pass Sprogø going east-west on the Danish E20 highway.