Using earlier sagas as his sources,
Snorri Sturluson gives a much more detailed account of Sigrid in several sagas within his 13th-century compilation, the
Heimskringla. He first introduces her in
Haralds saga gráfeldar, where he describes the upbringing of the Norwegian prince
Harald Grenske, who fled to Sweden and there joined the raiding band of
Skoglar Toste, described as the richest and most distinguished untitled man in the country, and staying with him the following winter. The saga then relates that Toste had a daughter Sigríd, who was young, fair and very haughty, and who later would marry Swedish king Eric the Victorious and become mother of King
Olaf the Swede. Snorri returns to Harald and Sigrid in the next saga in the
Hemskringla,
Óláfs saga Tryggvasonar. Now a wealthy queen dowager and mother of King Olaf, and described by Snorri as "the wisest of women and prophetic about many things", she learns that her foster-brother Harald is nearby on his way to raid in the Baltic Sea, and she invites him to a banquet, and afterwards personally serves him in his chamber. However, Harald took offence the next day when she favorably compared her own possessions and power in Sweden to his in Norway, leaving Harald sullen in spite of the great gifts she gave him. After stewing over this for a season, Harald again raided the Baltic and visited Sweden on his return. Sending for Sigrid, he proposed that they marry. She dismissed this, pointing out that he already had a wife, Asta, who seemed compatible with him, but he insisted Asta, though noble and good, was not as high-born as he. After a few further cursory words, Sigrid rode away, and Harald again turned sullen before deciding to ride to her home to press his case. Taking a large body of men, he arrived to find another suitor also present, a king called Vissavaldr from
Garðaríki. Both were housed in the same quarters, and served large quantities of drink, and then in the night she had her people set fire to the structure and kill anyone who made it out, declaring that this should prevent other petty kings from coming to her country to seek her hand. Snorri says that from thenceforth she was called
Sigríðr in stórráða, "Sigrid of the Great Undertakings". Sigrid makes one further brief appearance in the
Heimskringla, in
Magnúss saga ins góða. There she is described as mother of
Estrid Svendsdatter, the paternal (half-)sister of Cnut the Great and maternal half-sister of Swedish king Olaf. == Other appearances ==