Andvarnaut
an excerpt

The world of Nidavellir was not an entirely inviting place. Mountains and valleys shaped the landscape, giving it a cold, jagged demeanor. In spite of the rough appearance, down deep, underneath the harsh ridges, were the dwarf caves.
Dwarves were content to dig for gold and precious stones under the earth, and it would always be so; dwarves may never see the sunlight for fear of turning to stone. So it was with every dwarf, with one exception. Andvar, the gold smith, was a gifted dwarf. He would visit the outside world in the form of a fish, swimming swiftly from current to current in the underground lakes, finding inlets and following them until they met the open air and sun.