This is a four-issue arc against an enemy called Infinity. Basically, there’s some kind of void that was created when Hela tried to steal Odin’s life during his last Odinsleep.
It’s a big, broad, and cosmic story. One Jack Kirby would have drawn the Hell (or Hela) out of. Buscema’s art is certainly excellent, but it lacks the “bigness” of Kirby.
It all ends with a big cliffhanger: Because Infinity represented Hela’s failed attempt to claim Odin, she now goes after Thor…
For the complete history of the MU, year by year, go here.