The beginning of the story has the end of the big fight against the cosmic powered Hulk robot of the last two issues. That whole thing kind of fizzles out, I think it's safe to say that Kirby's heart wasn't in this plotline as much as most.
The battle does bring the Eternals into a long hidden underground lair, where an ancient enemy has been awakened. Ikaris is pulled under first, and Makarri follows. After Zuras stops a fire with his powers he follows.
He recognizes the enemy as Dromedan the Brain-Snatcher, who is forcing Ikaris and Makarri to fight each other. Zuras frees them of Dromedan's control and faces off against his old foe.
As I said, the Hulk robot thing ended weak, but the rest of the issue is stronger, especially the bits of Zuras' character. While obviously sharing some characteristics with previous Kirby god/rulers (Highfather/Odin/Zeus), he's a very different character in some fundamental ways.
Mike Royer inks the 17-page story and Frank Giacoia inks the cover (where "Ikaris" is spelled wrong).