Strange Tales #123 Aug 1964
"The Challenge of Loki!"
Dr. Strange practices the art of levitation; Meanwhile, in faraway Asgard, home of the Norse Gods, Loki, God of Mischief, plots as always;
He contacts Doctor Strange and tries to convince him that he is a prisoner of Thor, who is evil and deceiving his father;
Strange uses a spell to take Thor's hammer.
Script by Stan Lee and Steve Ditko (co-plot), pencils by Steve Ditko, inks by George Roussos (as George Bell)