The Swedes have a very famous temple called Uppsala, situated not far from the cities of Sigtuna and Björkö. In this temple, entirely decked out in gold, the people worship the statues of three gods in such a wise that the mightiest of them, Thor, occupies a throne in the middle of the chamber; Wotan and Frikko have places on either side. The significance of these gods is as follows: Thor, they say, presides over the air, and governs the thunder and lightning, the winds and rains, fair weather and crops. The other, Wotan – that is, the Furious – carries on war, and imparts to man strength against his enemies. The third is Frikko, who bestows peace and pleasure on mortals. His statue they fashion with an immense phallus. But Wotan they chisel armed, as we represent Mars. Thor, with his scepter, resembles Jove. The people also worship heroes made gods, whom they endow with immortality because of their remarkable exploits, as one can read in the Vita of Saint Ansgar they did in the case of king Eric.
For all their gods there are appointed priests to offer sacrifices for the people. If plague and famine threaten, a libation is poured to the idol Thor; if war, to Wotan; if marriages are to be celebrated, to Frikko. It is also customary to celebrate in Uppsala, at nine-year intervals, a general feast of all the provinces of Sweden. From attendance at this festival no one is exempted. Kings and people all and singly send their gifts to Uppsala, and, what is more distressing than any kind of punishment, those who have already adopted christianity redeem themselves though these ceremonies.
The sacrifice is of this nature: of every living thing that is male, they offer nine heads, with the blood of which it is customary to placate these gods. The bodies they hang in the sacred grove that adjoins the temple. Now this grove is so sacred in the eyes of the heathen that each and every tree in it is believed to be divine because of the death or putrefaction of the victims. Even dogs and horses hand there with men. A christian 72 years old told me that he had seen their bodies suspended promiscuously. Furthermore, the incantations chanted in the ritual of a sacrifice of this kind are manifold and unseemly; therefore it is better to keep silence about them.