This is the big Celestials story, which is started by Roy Thomas and John Buscema when comics were 35 cents and didn’t end for almost two years, when Mark Gruenwald and Keith Pollard had taken over and comics were half-a-buck. Was it worth all those issues?
Also, we get The Eternals folded into the main Marvel Universe. The Eternals were fringe characters before this story, and Roy Thomas kind of crowbars them into continuity using a very-heavily scripted story along with a full-page of text on a letters column, and it still doesn’t really make sense. We also get what amounts to a rehash of every issue of Thor so far, and learn that Thor’s mommy is Mother Earth.
Creators: Writing: Roy Thomas (#283-297), Ralph Macchio (#298, 301 (cowriter)), Mark Gruenwald (#299-301)
Art: John Buscema (#283-285), Keith Pollard (#286-289, 291-301), Arvell Malcolm Jones (#290).
For the complete history of the MU, year by year, go here.