Thor Annual#7(1978)

As Odin sends Hermod to Hel to see if there's anything to be done to save Balder, Thor begins wandering. He eventually finds himself in front of Mimir and asks the fiery guardian of the Well of Wisdom if Earth is doomed to die with Asgard in Ragnarok. When Mimir mentions that Thor, of all the gods, should know how the Earth will truly end, Thor doesn't understand what he means, prompting Mimir to mention that he had forgotten that Thor didn't remember certain events that had befallen him an Earthly millennium earlier. Mimir then begins to recount those events that began shortly after the brief war between the Asgardians and Olympians. Still wishing to extend Asgard's borders, the young Thor had left Asgard for Midgard. During his travels, he met the Eternals, learned of them, the Celestials and the Deviants, and fought several dangerous Mutates. Then, after Thor had spent months on Midgard, the starship carrying the Celestial Third Host arrived and Valkin, to prevent Thor from possibly doing battle with the Celestials, suppressed his memories of meeting the Eternals, the Mutates and the Celestials, and filled his brain with false memories instead. In the present, Thor has now regained those lost memories but is puzzled as to why they should matter when Ragnarok is so near. Mimir responds by showing him an image of a scene occurring at that moment in the Andes Mountains of South America: Arishem of the Fourth Host standing unmoving as he prepares, in less than fifty years, to judge whether on not Earth shall perish at the hands of the Celestials.