In Marvel, it is Odin, Thor's father, who was responsible for instructing the dwarves Eitri, Brokk and Buri to forge the hammer from a chunk of Uru. The origins of the weapon vary between Marvel and ancient myths but the power levels of the weapon are similar - this is essentially a nuclear powered lighting boomerang, that just so happens to be shaped as a hammer. Mjolnir is an iconic weapon of the Norse God of Thunder.
