Origin: Mjolnir was forged by Odin and the Dwarves Eitri, Brok, and Buri. The mold/forge for the hammer was the core of a star, which exploded during the process; it is believed that this star exploding is what caused the extinction of the dinosaurs. Laufey the giant was slain by Odin with this hammer, which was later bequeathed to Thor. The hammer's history and that of Thor are intertwined from that point on.
Type: Enchanted War hammer of the gods.
Powers and Abilities: Mjolnir has had many enchantments placed on it by Odin. One of the primary of these is the Worthiness enchantment which makes it so that only certain people, those who are found worthy, can wield it. Few have held it aside from Thor.
Captain America after wielding the power of Mjolnir and Thor said "I've never wielded such limitless power before!" "It's almost intoxicating!"
The Worthiness enchantment can be bypassed by Thor who can bequeath it to others if need be. However, the enchantment has altered since the original time: Curently, due to the link between it and Thor, no other can weild it as long as Thor lives.
This link also allows the Hammer to return to Thor no matter what is between him and it. The hammer will plow through planets and stars to return to Thor's grasp. Various times the hammer has also allowed transformation to his mortal form.
Being made of Uru, the hammer is also the perfect mechanism for energy/magic manipulation absorption and redirection. The hammer is capable of channeling even enough energy to destroy planets.
It is also a perfect medium for the natural powers of the god of thunder. Thor is able to channel his weather and earth manipulation powers through and with the hammer. While he does not need it, the hammer also grants the power of flight.
Mjolnir has also shown matter and soul manipulation, the ressurection of people, and control of the magnetic spectrum. It also allows invisibility, intagibility, teleportaion, transformations, and the draining of life force.
Destructive Capacity: Planetary destruction, however it has contained the energy to destroy galaxies before thus it may be capable of that level of destruction.
Temporary Wielders/those deemed worthy: Tiwaz, Bor, Odin, Beta Ray Bill, Red Norvell, Eric Masterson, Ororo Munroe, Steve Rogers, Simon Wiliams, Alexander Power.
Material: Uru metal, a nearly indestructible metal from Asgard that is especially adept at absorbing magic and energy, almost like a sponge.
Needed Prerequisites for use: Being Thor, Thor's Death, proving worthy, time of need so dire Odin will lift the enchantment for you.
Notable attacks/techniques: See powers. Specific ones include bludgeoning, lightning blasts, ability to fly at superluminal speeds, and creating cracks in planets.
Alternate Forms: Every alternate version of Thor has an alt of Mjolnir.
Similar Weapons created in it's image for worthy ones: Crusher for Red Norvell, Stormbreaker for Beta Ray Bill, and Thunderstrike for Eric Masterson.