The Viking Age saw the last stand of paganism in Scandinavia, where raiding and trading brought followers of a pantheistic religion into contact – and often conflict – with Christian and Muslim worshippers of a monotheistic God.

What we know of the gods and creation myths of the Vikings has been passed down by certain texts such as the 'Poetic Edda' (an unnamed collection of anonymous Old Norse poems), and ‘Heimskringla’, by Snorri Sturluson, who was a Christian.

For the Vikings and their ancestors, the universe began with the two elements of heat and cold, with Ginnungagap in between, and life beginning where the two elements met; where the titan Ymir was formed.

Audhumla the cow suckled the young Ymir and licked the ice to create Buri, who went on to be the grandfather of Odin, Vili and Ve. These three then killed Ymir, whose body formed the earth and his skull the sky, while one of his eyebrows formed a wall to separate the world of the giants from Midgard, the world of men.

At the centre of this universe was Yggdrasill, a gigantic ash tree with three roots: one in Asgard – the land of the gods (the Aesir); one in Jotunheim – the land of the frost giants; and the other in Niflheim – the world of the dead. Near these roots are three wells: Hvergelmir, in which Nidhogg lived (the serpent that gnawed at the tree’s roots); Mímisbrunnr, the source of wisdom (Odin sacrificed an eye for its waters); and Urdarbrunnr, the Well of Fate, from which the tree is watered by the three Norns (the Fates) – Urd, Verdandi and Skuld.

The tree united the nine Norse homeworlds and was populated by various animals, including an eagle in its topmost branches that had a falcon sitting between its eyes and traded insults with Nidhogg, via Ratatoskr, a squirrel who scurried between the two.

The leader of the gods was Odin, who married the goddess Frigg. Below them were lesser deities such as Thor (god of thunder), Tyr (god of war), Loki (god of fire), Frey and Freya (gods of fertility), Aegir and Njord (gods of the sea), Bragi (god of poetry), Ull (god of archery) and Hel (goddess of the underworld).

Different gods seem to have held sway in different parts of Scandinavia. For instance, Odin was paramount in Sweden and Denmark; Thor was widely worshipped in all three countries apart from the area around Trondheim in Norway; Tyr was popular just in Denmark, and Frey in Sweden.

One of the most important centres of Scandinavian paganism was the temple at Uppsala in Sweden, just north of modern Stockholm, which is surrounded by the burial mounds of ancient kings who were interred with their horses, dogs, servants and weapons.

Adam of Bremen described the biggest festival taking place at the vernal equinox every nine years, where nine of every male animal were sacrificed. The carcasses were hung in a sacred grove next to the temple, with human corpses hanging next to dogs, horses and other animals.

Adam also spoke of three images in the temple, of Thor, Odin and Frey, who would be sacrificed to, respectively, in times of blight and disease, war, and at weddings. Thor was the god of strength and wielded the hammer, Mjollnir. Odin, being the god of battle, alone could give victory or defeat. Frey’s image had an over-sized penis as he was the god of fertility. Odin’s servants were the Valkyrie, female entities who conducted those warriors slain in battle to Valhalla to feast in Odin’s great hall until Ragnarok.

Three major religious festivals were held each year, one at the beginning of summer, one in autumn and one at midwinter. The summer feast was closely associated with bringing good fortune and victory for the coming raiding season, and sacrifices for victory were duly made.

Slaves were often sacrificed on the death of their master, to accompany him on his journey to Valhalla. The Arab diplomat, Ibn Fadlan, describes in detail the ceremony of a Rus burial on the banks of the Volga in 922, which ended in the killing of a slave girl who volunteered to join her late master on his funeral pyre.

Christian missionaries were converting Viking pagans from 825 onwards, when Louis the Pious dispatched priests such as Anskar to thriving communities like Hedeby. The process would be a long one, with various rulers such as Harald Bluetooth bringing Denmark into the Christian realm over a hundred years after the first conversions. The lands to the north remained stubbornly heathen, but the writing was firmly on the wall for the old gods.