That is one crowded cover!
The Story: "Crisis in Eternity!" by E.Nelson Bridwell, Martin Pasko, Dick Dillin, and Frank McLaughlin. Members of the JLA, JSA, and heroes from Earth-S are rounded up by someone who looks a lot like the Greek god Mercury(!) to stop a plot hatched by the evil King Kull.
Superman and the Earth-2 Wonder Woman head to Earth-2 where they take on Ibac, Blockbuster, and...The Penguin? Oh, the horror!
As they take on the Blockbuster, Ibac and the Penguin build a device--ordered to by Kull--that creates a cloud that floats over the island of Atlantis and tries to sink it back into the sea!
Luckily Superman uses his super-breath to freeze the cloud into a block of ice, which he the hurtles into space. Unfortunately, though an earthquake hits, dropping it back into the sea from whence it came.
Kull is mad his plot has been foiled, but promises even greater doom for Earths 1 and S. To be continued!
Roll Call: Superman, Flash, Green Lantern, Green Arrow, Hawkman
Notable Moments: Hawkgirl guest-stars again, as does a bunch of Fawcett heroes, like Bulletgirl, Bulletman, Ibis, Mr.Scarlet, Pinky(!), and Spy Smasher. Was Dick Dillin getting too far ahead on his deadlines?
I read this issue twice through in preparation for this post, and still couldn't figure out all that is going on. There's so many characters, so many locales that at some point I gave up and went right to the Answer Man column.