His Bio, found in Facebook Game Wall Posts, states that his name is "Ragnarok". As he is the clone of Thor, he is Thor's counterpart in the Dark Avengers.
Dark Thor's sprite is wearing one of Thor's original outfits in the comics, which hinted to the future design of Thor's Mighty Thor Alternate Uniform in the game.
The title of Task 22 in Special Operations - Dark Reign references the comic panel between Hercules and Dark Thor during the Civil War Story Arc. The Task's title, "Thou Art No Thor" is said by Hercules to Dark Thor.
He is first officially referred to as Ragnarok in the game in the mission description for Season 2, Chapter 5, Mission 5.