Brísingamen

In Norse mythology, Brísingamen (from Old Norse "brísinga" meaning "flaming, glowing" and "men", meaning "jewellery, ornament") is the necklace of the goddess Freyja.

Myths & Legends
One day when she was out walking, Freyja came the residence of some dvergar. The door was open and Freyja entered. Once inside she saw the most beautiful necklace she had ever laid her eyes on. The four dwarfs living there had made it; dwarfs were masters of craftsmanship. Freyja begged to purchase the necklace. The dwarfs would not sell it for any amount of gold. Freyja asked them to name their price. They replied that she may keep the necklace if she would spend one night with each of the four dwarfs. Freyja went along with the deal. After four night of lovemaking, she walked away with the necklace. That is how Freyja became the owner of Brísingamen.

Theft
The necklace was stolen by Loki in the guise of a fly. Freyja enlists the help of Heimdallr to find it. Loki is found by Heimdallr and both turn into seals and fight. When Heimdallr eventually, wins he returns the necklace to Freyja.

Other Uses
When the Jǫtunn Þrymr steals Þórr's hammer Mjöllnir, Þórr dresses as Freyja in an attempt to win it back. As part of his disguise, Thor borrows Brisingamen.