King Magnus IV of Sweden, also known as Magnus Ladulås, reigned from 1275 to 1290. He was a member of the House of Bjelbo and is known for his efforts to strengthen the monarchy and centralize power in Sweden. Magnus IV implemented various reforms, including the establishment of a more organized legal system and the promotion of trade. During his reign, Magnus IV also focused on expanding Sweden's territory and influence. He was involved in conflicts with neighboring regions, particularly Finland and Norway. His reign is often seen as a significant period in the development of the Swedish state.