Jafnadr is a famous sword, blessed by the Goddess Malfin - Goddess of the Darkness. The name, in translation, means both equality and justice. It was made for Jafnadr, the daughter of Malfin - Goddess of the Darkness and fafnir by frijdodr.
Like a slice of darkness. It is completely black, and the blade absorbs light, apart from a round matt white stone on the pommel. It can also disguise itself when asked to so that people don’t notice it (it still looks like a sword, but not a remarkable one).
It is super sharp, and will slice through armour like it isn't there. Also Jafnadr absorbs the memories of its wielder, and those in the close vicinity (albeit more slowly, and it can have difficulty with anyone attempting to resist or with significant divine powers). As a sentient sword it can speak to its wielder via a mental link, but only when the wielder is touching any part of the sword.
Only those descended from the original owner, Jafnadr (a daughter of Malfin and Fafnir) can use it. Additionally it needs to be used without malice.
Currently Yngvild Helgasdotir is the wielder of Jafnadr, she inherited it from her father oddmundr (who she has never met).