Collecting Thor (1966) #154-174.

From the darkened depths rises a peril greater than any Thor has ever before faced. Mangog threatens to unsheathe the Odinsword and bring Ragnarok upon the Norse gods in this collection of Asgardian classics! Plus, a cosmic battle between Galactus and Ego the Living Planet; the return of "Him," the man who would come to be known as Adam Warlock; and the universe-shaking origin of Galactus! Thor's adventures get personal, too, with a surprising revelation regarding Donald Blake, the return of Jane Foster, and the dramatic dance between Balder and the Norn queen Karnilla!