Harald and Magnus have separate courts and keep to themselves during their short co-rule, and their only recorded meetings nearly end in physical clashes.

Magnus and Harald go to Denmark in 1047, with their leidang forces.

Magnus, however, dies suddenly on October 25 while in Denmark, either in Zealand or in Jutland, either in an accident or of a disease; accounts vary.

Reports include falling overboard from one of the ships he was mustering to invade England and drowning, falling off a horse, and falling ill while on board a ship.

He is said to have made Sweyn his heir in Denmark, and Harald in Norway; some say in a deathbed statement.

Upon hearing the news of Magnus's death, Harald quickly gathers the local leaders in Norway and declares himself king of Norway as well as of Denmark.

Although Magnus had appointed Sweyn his successor as king of Denmark, Harald immediately announces his plans to gather an army and oust his former ally from the country.

In response, the army and the chieftains, headed by Einar Thambarskelfir, oppose any plans of invading Denmark.

Although Harald himself objects to bringing the body of Magnus back to Norway, the Norwegian army prepares to transport his body to Nidaros (now Trondheim), where they bury him next to Saint Olaf in late 1047.

Einar, an opponent of Harald, claims that "to follow Magnus dead was better than to follow any other king alive". (Tjønn, Halvor (2010). Harald Hardråde. Sagakongene (in Norwegian). p. 103. Saga Bok/Spartacus)