Thor (1962) #240
"When the Gods Make War!" is written by Roy Thomas and Bill Mantlo with art by Sal Buscema and Klaus Janson. Cover by Gil Kane. The Asgardians call Odin the "All-Father" and now they know just how true that may be. A trio of Egyptian gods trapped inside an indestructible pyramid kidnap the amnesiac Odin from California's grape vineyards and convince him he is Atum-Re, the Father of all Gods. Osiris, Isis and Horus need Odin to be Atum-Re for them to break the curse placed by Horus' murderous half-brother Seth.
Thor discovers their treachery when a journey to Asgard reveals all of the gods there to be under some sort of spell of listlessness. Heimdall, the legendary guardian of the Rainbow Bridge, is deaf and weak. The Warriors Three stumble about without purpose. Only by consulting the ancient fiery font of knowledge known as Mimir can Thor uncover the fate of the missing Odin. Once he finds his father, however, Thor must battle Horus, his counterpart in the Egyptian mythos and then, eventually, Odin himself!