1064 – He was born this year in Denmark. He was presumably the youngest son of King Sweyn Estridson and married Margaret, princess of Sweden, with whom he had Magnus the Strong.
1103 – Four of Niels’ older brothers had ascended to the throne before him, and when Eric I "The Evergood" died in July 1103 during a pilgrimage. Niels or Nikolas became King the following year.
1131 – But after 26 years of peace, Niels’ son Magnus had reached adulthood, a conflict erupted between him and his cousin Canute (Knud) Lavard, the son of Eric "Evergood". Canute was employed as king Niels’ earl, and Magnus (rightly) viewed Canute as a likely contender for the throne once the aging king died. On the 7th day of January of this year, he slew his cousin near Haraldsted just north of Ringsted, and a civil war ensued as Canute’s half-brother Eric tried to avenge his death and secure the throne for him in the process.
1134 – The church and seemingly most of the Danish public still supported king Niels, and Eric made little progress, being forced at last to flee to Sweden in this year. However, when Niels and Magnus landed at Fodevig bay in Scania just before midsummer, determined to finish off Eric once and for all, they were taken by surprise by a contingent of German soldiers on horses, Niels’ army were slaughtered before they had time to regroup, and Magnus was slain. King Niels himself escaped alive. Finally, king Niels himself was felled, and thus ended the reign of the last of Sweyn Estridson’s sons.