[1] The saga was written by the Icelandic historian and chieftain Sturla Þórðarson.
Sturla was in Norway in 1278, and it is assumed that he started work on the saga then, on request of King Magnus himself.
In addition, some passages were copied into Icelandic annals, and have thus been passed down to us today.
The small fragments we have show us glimpses of a realistic narrative style, written in strict chronological order, reminiscent of Sturla's work in Hákonar saga Hákonarsonar.
It is not known whether the narrative started with Magnus' accession to the throne upon his father's death, thus continuing the narrative of Hákonar saga Hákonarsonar, or whether it started with Magnus' birth, as the beginning of the saga is not preserved.