 In later Scandinavian practice, human sacrifice appears to have become more institutionalised, and was repeated as part of a larger sacrifice on a periodic basis (according to Adam of Bremen every nine years).Evidence of Germanic practices of human sacrifice predating the Viking Age depend on archaeology and on a few scattered accounts in Greco-Roman ethnography.For example, Tacitus reports Germanic human sacrifice to (what he interprets as) Mercury, and to Isis specifically among the Suebians.