Sacred broadsword of the Ragnarsson Clan of Nilfeheim. The original broadsword was made by a small Swedish sword making company of Earth. Commisioned by Eric Ragnarsson before he left Earth aboard the Ark Stockholm to settle on Nilfeheim in 2160.
The original sword (like 250 similar swords) was made out of the then new material Ultronit,an almost indestructible steel cobalt carbon alloy and was called "The Killer" in Swedish (Mördaren). Both names : Mördaren and Mjördaren are used depending on the dialect ( The first original Swedish and the second "Nilfeheim Norsk")
It was handed down in an uninterrupted chain from Generation to Generation of the Ragnarsson's until it reached Erik Gustav Ragnarsson. At least that is what the Ragnarsson Clan believed.
The truth is that the real Mjördaren, the one manufactured on Earth never made it aboard the Ark.
An Immortal called Richard Jorgensen tasked by the Guardian switched the swords with an Artifact called Dark Blade. (One of the 12 Tokens of Power that belong to the Dark Master (the Dark One)).
Dark Blade moe than a weapon or a piece of metal is not easily understood, but it appears to be the "Evil" soul part of the Dark One and has a concious of its own. It is not known if it is a techncial product, a being of some kind or a mystical thing of unimaginable power. It beyond the capabilities of a Techlevel 12 civilization. The Blade disguised itself as Mjördaren and waited until the Dark One was reborn in Eric Olafson.
The sword always had "mystical" powers and loved to "drink Blood" accroding to its many owners and it could only be wielded by a real Ragnarsson. When it reached the last Ragnarsson in Erik Gustav it was handed to Eric Olafson, the true owner the sword waited for.Tyr, the white Tyranno manages to seperate Eric from the blade as he gained it too early and its evil nature would influence him too strongly when he had to make his decission.
(The sword slowly but surely raised the lust to kill and maim in Eric.)
Tyr replaces Dark Blade / Mjördaren with a very good replica made by him. Eric hands this (3rd) Mjördaren to Sif , without knwoing that there are two others.
Eric later rediscovers Dark Blade and forgets about Mjördaren.
Sif finds the real Mördaren in a cave on Earth and handed both replicas to her children twins Eric and Freya.