Magnus spent his time in Venice and Rome, where he wrote two historical works about Sweden: "Historia de omnibus Gothorum Sueonumque regibus" and "Historia metropolitanæ ecclesiæ Upsaliensis", which are important for their historical information, but are also filled with tales that have no reliable foundation.
В Риме и Венеции епископ-эмигрант написал две книги: "Historia de omnibus Gothorum Sueonumque regibus" («История всех королей готов и шведов») и "Historia metropolitanæ ecclesiæ Upsaliensis" («История митрополии Упсальской»).