 During the Early Middle Ages the papacy had not yet manifested itself as the central Roman Catholic authority, so that regional variants of Christianity could develop.Since the image of a "victorious Christ" frequently appears in early Germanic art, scholars have suggested that Christian missionaries presented Christ "as figure of strength and luck" and that possibly the Book of Revelation, which presents Christ as victor over Satan, played a central part in the spread of Christianity among the Vikings.Recorded missionary efforts in Denmark started with Willibrord, "Apostle to the Frisians", who preached in Schleswig, which at the time was part of Denmark.