I just read “The Pretenders,” a play by Henrik Ibsen. It is a fictional account of the tortured relationship between Haakon IV and Earl Skule Baardsson, who was chosen by the Birkebeiner council to rule as regent for Haakon until he came of age, and to permanently rule 1/3 of the kingdom. By some accounts, it was Skule who actually accomplished many things that are usually credited to Haakon.
Years later, Skule Baardsson ended up rebelling and being put to death, and Ibsen makes a great fiction of it, complete with an arch-evil bishop (or was it an evil archbishop?). The opening scene is the mother’s trial by ordeal, which in the play is just the first of many ordeals.
Many basic facts are true, e.g. Haakon married Skule’s daughter Margrite to try to keep the earl on board (this fact makes Skule Baardsson my ancestor). The timeline may have been altered a bit, and some elements were no doubt made-up. But the best part is the (wholly fictional) dialogue and the vivid, three-dimensional characters. Quintessential Ibsen; I read it in one long sitting. Google books has it for free (English translation of course – as if I could read anything else!)