Short answers, pulled from the story.
Olaus Magnus (born Olof Månsson in Linköping in October 1490) was a Swedish Catholic clergyman, cartographer, and writer who spent much of his life in exile. He is best known for producing the Carta marina in 1539 and the Historia de Gentibus Septentrionalibus in 1555, the latter of which became the primary European authority on Scandinavia for generations.
The Historia de Gentibus Septentrionalibus, printed in Rome in 1555, is a patriotic work of folklore and history describing the customs, superstitions, animals, and geography of northern peoples. It was translated into Italian (1565), German (1567), English (1658), and Dutch (1665), but not into Swedish until 1909.
The Carta marina is a large map of Northern Europe created by Olaus Magnus in Venice in 1539, with the financial support of Hieronymo Quirino. It measures 125 cm tall and 170 cm wide across nine parts, and was rediscovered by Oscar Brenner in the Munich state library in 1886, where it was identified as the most accurate depiction of Scandinavia of its era.
Olaus Magnus was exiled because his loyalty to the Catholic Church made him incompatible with the Protestant Reformation that took hold in Sweden. He remained abroad in Poland rather than abandon his faith, and his Swedish belongings were confiscated in 1530.
Pope Paul III appointed Olaus Magnus as Archbishop of Uppsala in 1544 following the death of his brother Johannes Magnus, who had previously held the position. The title was nominal because Sweden was no longer Catholic and Olaus remained banished from the country.
Present-day oceanographers rediscovered that Olaus Magnus had accurately depicted the ocean currents between Iceland and the Faroe Islands in his Carta marina. Setting aside the decorative sea monsters, his observations were precise enough to generate a series of scientific publications citing his sixteenth-century records as valid data.