Ragnarök: The Breaking of Helheim (Ragnarök: The Breaking of Helheim #2)

Thor begins his descent into the Kingdom of the Dead, but finds the way blocked by a titanic Hall rising before him on the rim of Helheim. Guarded by both the living and the dead and ruled by the iron hand of a would-be god, it hides beneath its deepest dungeons a secret powerful enough to shatter the very foundations of the Dusklands.