@sweetpea_gal - We have a winner!  Get that gal a George Foreman grill or something!

@REXONANDO - Well, here's what Wikipedia has to say on the matter.  Personally, I like the part where Dr. Doom is escaping Hell as Mjolnir just sorta happens to be in the neighborhood, so he's all "Eh, why not.  I'll give it the old college try!"

Anyway, Wiki's explanation:

"Thor learns that the Ragnarok cycle is the result of self-styled "gods to the gods" known as Those Who Sit Above in Shadow, who feed on the cycle. Thor confronts the Norns (Fates), breaking the Ragnarok cycle, and then enters a stasis, sleeping "the sleep of the gods." With his fate unknown to the Avengers, he is believed to be missing in action.[28]

Thor's hammer Mjolnir is found on Earth and put under U.S. Army protection. Sometime later, the supervillain Doctor Doom is escaping from Hell as Mjolnir falls through that dimensional plane, and tries unsuccessfully to claim the hammer, which eventually comes into the possession of a man carrying a bag with the initials "D.B".[29] During a battle in the superhero "Civil War" between pro- and anti-Superhuman Registration factions, Thor seems to appear and kills the superhero Goliath.[30] This "Thor" is later revealed to be a fusion of cloning technology and cybernetics created by scientists Reed Richards and Henry Pym, and is destroyed by anti-registration superheroes Storm and Hercules.[31]

Donald Blake, upon touching the hammer Mjolnir, is transported to the void where Thor has been in hibernation. Blake explains that when Odin originally removed the Blake persona from Thor,[32] Blake was transported to the void Thor now inhabits, and was returned to New York City when Thor broke the Ragnarök cycle. Blake convinces Thor to wield Mjolnir once more, return to Earth, and renew the dual identity with Blake. Blake also reveals that Thor's fellow Asgardians are not dead but hidden on Earth.[33]"