|Holding hot iron in a Trial by Ordeal.|
The post linked above mentioned how Haakon III died without an heir, so a nephew named Guttorm Sigurdsson was put on the throne of Norway. He was only four years old, and so the responsibility of governing was put into the hands of regents. Guttorm only lived as king a few months, actually, dying of an illness (remember the sudden illness that killed his predecessor? it seems to have been a trend in Norwegian politics of the 13th century). One of his regents was Haakon the Crazy.
To give this new Haakon the benefit of the doubt, what we translate as "crazy" would probably more appropriately be defined as "furious in battle" than "unstable of mind." He was a supporter of King Sverre (Margaret's husband), and was made regent for Guttorm and leader of Norway's armies at the death of Sverre's son, Haakon III. Unfortunately, he had connections with Sweden that made him unsuitable for king, so at Guttorm's untimely death, Haakon the Crazy's half-brother Inge became king.
Haakon the Crazy died at the end of 1214; King Inge died in April 1217; and here's where it gets more interesting. A woman whom Haakon III had taken as a concubine in 1203 appeared in public with her young son, claiming that he was a son of Haakon III. Normally, this would not necessarily carry any weight, but she decided to go through a Trial by Ordeal. She carried a piece of hot iron without apparent damage from the heat, proving before all of Sweden that her claim of proper paternity for her son was true!
The boy, Haakon, became King Haakon IV and reigned from June of 1217 until his death on 16 December 1263. His reign is considered a golden age of medieval Norway.