Mjölnir, in Norse legends was a powerful weapon or rather a hammer, of the thunder god, Thor.
The hammer never failed him. He used this hammer to fight against the giants and used to crash their heads with this hammer.
Modern Vikings wear Thor's hammer necklace and Thor's hammer pendant as a symbol of power and boldness. In Norse mythology, Thor's hammer was his source of power and it never let him lose in the battles against the giants.
The story of Thor's hammer is an interesting one, for modern Vikings as they tend to include Thor's hammer shape in the Viking jewelry such as Viking ring, Viking bracelet and Viking arm rings. The culture runs in the blood of the Vikings and the story of creation of Thor's hammer would enlighten the belief and faith of the modern Vikings.
CREATION OF THOR'S HAMMER
One day, Loki, the trickster noticed the beautiful golden hair of the wife of Thor Sif. His mischievous personality urged him to cut off her hair. When Thor came to know of this, he was enraged with anger and threatened Loki that he will tear him apart, limb to limb. Loki immediately negotiated with Thor and requested him to let him go to Svartalfheim, the cavernous home of the dwarves. As Loki was pleading, Thor allowed him to go there and asked him to return with even a more beautiful piece of golden hair for his wife, Sif.
There he went to the sons of the dwarves. Ivaldi was successful to create him a new head of hair along with other marvelous creations, that is the Skidbladnir, the best of all ships and Gungnir, the deadliest of all the spears, ever created. The ship could be even folded into a pocket and when on sea, will always have a favorable wind. The spear if taken to a battle would never miss its hit.
As he was leaving, Loki was overcome by an urge to stay. He went to the other sons of the dwarves, Brokkr and Sindri, and mocked them about their inabilities. He taunted them that they would not be able to forge such creations that Ivaldi has created. He even challenged them and bet his head on this. Brokkr and Sindri accepted the wager in rage and began working to create more marvelous creations.
As they worked, Loki turned into a bee and stung Sindri's hand. When Sindri pulled the gold out of the fire, it was a living boar with golden hair, known as the Gullinbursti. It could guide the way at night and ran faster than any horse.
Sindri again set the gold on fire and the bee again stung Brokkr's neck. This time, when the gold was pulled out of the fire, it turned out to be a magnificent ring, which could replicate itself 8 times, on every ninth night.
When Sindri and Brokkr again put the gold piece into the fire, Loki immediately bit on Brokkr's eyelid. It became impossible for Brokkr to see his invention. Sindri unintentionally produced a hammer of unsurpassed quality, which would never miss its marks and will always boomerang back to its owner. But, it had one flaw. The handle was short. Sindri called it, the Mjolnir. Nevertheless, the two sons picked up their creations and set their journey to Asgard, to claim their wages that were due to them.
Loki made to the Asgard way before the dwarves and presented Thor, with the hammer and the new head of hair. He gave the ring to Odin and the spear to Draupnir. He gave the Gullinbursti and Skidbladnir to Freyr.
The gods were very happy with the creations, especially the Mjölnir, as it could be used in battles against the giants to smash their heads. But, Loki still owed his head to Brokkr and Sindri. One of the cunning god pointed out that they should get the head and not the neck. Upon which, the dwarves sew Loki's mouth shut and returned to the caves. Thus, this is how Thor's hammer was created in Norse legendry, which the Vikings still use as a symbol of power.