Near the end of his life, Henry IV devoted more and more time to hedonistic luxury, while Magnus and his brothers Albert and John took over the most active share in the business of government.
John died in 1474 leaving a grieving widow, Sophie of Pomerania-Stettin, daughter of Eric II of Pomerania, whom Magnus married himself on 29 May 1478.
Magnus reigned until his death in 1503, when he was succeeded by his sons Henry V, Eric II and Albert VII, who at first ruled jointly until they split their lands into the duchies of Mecklenburg-Schwerin and Mecklenburg-Güstrow in 1520.
In the end, rebel leader Hans Runge and three other insurgents were executed and the city had to recognize the cathedral chapter, pay a substantial fine and confirm all of the Duke's privileges.
The excommunication and interdict under which Magnus and Balthasar had been placed by Holy Roman Emperor Frederick III and Pope Innocent VIII were then rescinded.
After Magnus' death, his youngest daughter Catherine achieved fame in her own right as the mother of the famous Duke Maurice of Saxony.