A little bit of Norse mythology
, its name means 'the necklace of the Brising
Like most of the jewelry in Asgard, this necklace was created by the dwarves (In this specific case, Alfric, Berling, Dvalin, and Grer). The four dwarves demanded that Freya should spend a night with each of them as payment. No problem, Freya is, after all, the Goddess of Love.
Enter Loki. He heard of Freya's deal with the dwarves and decided to inform Odin. Odin punished Freya by forcing her to start a war between two human kings.
As many of the other (Gungnir, Mjölnir etc) items created by the dwarves, Brisingamen had magical powers - it protected the wearer from harm, a feature that the weak Freya would benefit from. Greedy Loki decided to steal the Brisingamen, entered Freya's castle Folkvang by transforming into a fly, transformed into a louse and bit her so she turned over in her sleep, allowing Loki to remove the necklace. Loki then hid the necklace at an islet called Singasten.
Word of the theft spread all over Asgard, and soon reached Heimdall, who immediately suspected the trickster Loki. Heimdall travelled to Singasten, located Loki - who had transformed into a seal, tranformed into a seal himself and challenged Loki. Great Old Norse Epic Battle followed.
Heimdall defeated Loki and brought the Brisingamen back to its rightful owner.