The Great Blot at Uppsala

The single most detailed surviving account of pre-Christian Scandinavian sacrificial practice comes from Adam of Bremen, a German cleric writing in the 1070s CE, describing a great festival held every nine years at the royal temple of Uppsala in Sweden. According to Adam, the rite lasted nine days, during which sacrifices were offered from every living species, animal and, he states, human, with nine males of each kind killed and their bodies hung in the sacred grove that stood beside the temple, a grove Adam describes as so hallowed by the presence of the dead and dying offerings that ordinary people avoided walking beneath its trees.

Adam links the temple itself to the worship of three principal gods, whom he names as Thor, Wodan and Fricco, generally understood as Thor, Odin and Freyr, describing their images enthroned together inside the building and noting that different petitioners favored different gods depending on their need, Thor for plague or famine, Wodan for war, Fricco for marriage and fertility, a division of divine responsibility that broadly matches patterns found elsewhere in the surviving Norse mythological corpus. Adam himself never claims to have witnessed the nine day rite firsthand, and the numeral nine recurs suspiciously often in his account, in the years between celebrations, the days of sacrifice and the victims of each kind, a repetition some modern scholars read as owing as much to the number's symbolic weight in Adam's own sources as to a precise historical count.

Adam of Bremen never visited Uppsala himself. He compiled his account from informants, including, by his own claim, a Christian eyewitness who had reportedly counted seventy-two bodies hung in the grove, and he wrote as a cleric of the archdiocese responsible for missionary efforts in Scandinavia, with an obvious interest in portraying the paganism his church was working to displace as both impressively organized and appropriately shocking to a Christian readership. Modern historians treat his account, accordingly, as valuable but not straightforwardly reliable, likely combining genuine informant testimony about a real and significant cult site with rhetorical elaboration suited to Adam's own purposes, and archaeological work at Gamla Uppsala has confirmed the site's importance as a major cult and burial center across the Iron Age and Viking Age without being able to confirm every specific of Adam's description.

Whatever the precise historical accuracy of the nine-year cycle and the exact numbers involved, Adam's account remains the fullest surviving description of any Norse pagan sacrificial festival, and its combination of periodic timing, animal and reportedly human sacrifice, and a dedicated sacred grove attached to a major temple complex is treated by scholars of Norse religion as broadly consistent with what other, more fragmentary sources suggest about how the largest Scandinavian cult centers conducted their most important collective rites.