The Vikings were fearless warriors, traders and explorers. But few realize their restless spirits were guided by powerful women.

Seers and sorceresses known as "volvas" played a central role in Norse society and a spotlight is finally being shone on their shadowy influence in a ground-breaking show at Denmark's National Museum.

The volvas were "a kind of female shaman, a seeress, a spy woman", said Peter Pentz, a researcher who helped curate the show. They could "look into the future, fly... and foretell your fortune," he told AFP. 

They could even summon the gods, according to the sagas, the oral accounts of the Viking age from the 9th to the 11th century, which were written down hundreds of years later. 

The exhibition is the first in the museum's history to focus on one particular woman, said Pentz standing in front of a case containing the remains of a volva exhumed from a ring fort built for Harald Bluetooth, the legendary Danish king who gave his name -- and his runic initials -- to bluetooth technology.

"We believe that she might have been the king's advisor," he said.

Visitors to the show are plunged into the fantastical universe of the volvas, with Viking jewellery, amulets, rune stones, sagas and other archaeological finds on display.

'Psychedelic seeds'

"The word 'volva' means staff bearer," Pentz said. In northern Europe, women often held senior roles in society, enjoying more rights than their counterparts in the Mediterranean or the Frankish empire, he insisted. 

"For instance, they would have had the right to seek a divorce" if their husbands were violent towards them, he said.

In addition to her iron staff, the volva in the exhibition was buried with a purse containing seeds from a plant likely to help her fall into a psychedelic trance to see the future.

She was also buried with other objects from afar.

"Artefacts coming from faraway bring mystical knowledge," Pentz said.

Despite the volva's prominent role, they were marginalised women, Pentz said, although they did not suffer the stigmas that were later applied to witches in Europe.

"They were either widows or unmarried women. And they stood outside the farm, which was the basic unit of Viking society."

With the arrival of Christianity, the volva's role faded and they were forgotten until academics began studying the Icelandic sagas.

"The functions of the volva were given to many other characters in medieval society," including priests, Pentz said.