Druig's Eternals attacked Krakoa (the mutant island) and Arakko (the transformed Mars) because the mutants were examples of Excess Deviation. The 'good' Eternals and the Avengers with mutant Mister Sinister brought the Avengers HQ (the body of the dead Celestial named Progenitor) back to life. It stopped the war but then decided to judge everyone on Earth in the next 24 hours. Last issue MrS secretly told the X-Men how to destroy the Celestial but they failed. But then Sersi implemented her own plan by releasing Eros/Starfox from his Exclusion prison.
Faced with the end of the world humanity reacts by turning on itself. Captain America (already judged a failure) tries to stop mutant-haters storming the Krakoan embassy in New York. But he's overwhelmed by numbers.
Meanwhile in their bunker outside the transformed HQ the conspirators (Mr Sinister, Iron Man of the Avengers, and the Eternals Ajak, Makkari and Phastos) who created the new Celestial god meet with Sersi and Starfox to hear the plan. The Titanian is enough of an Eternal that the Great Machine accepts him. Sersi proposes that Eros uses the Machine to broadcast peace and love throughout the world. This will fool Progenitor into letting the majority pass his test, and that means *everyone* gets saved. But Starfox thinks that fakery will just make everyone *fail*. The voiceover of the Celestial, who knows everything that's going on, tells us he agrees with him. So SF has another plan.
We see Progenitor, while his physical body remains at the North Pole, appear in various guises to judge various people all over the world, including the 6 humans the voiceover introduced to us in #2. Bigoted Tom in London is a judged negatively because he failed to see the irony of being beaten up by 2 men who thought he was a foreigner. Katrina in Vancouver also gets the thumbs-down, from the image of her dead Aunt, because she's in too much of a hurry to leave a tip. Arjun in Mumbai died so the Celestial takes pity on his widow and doesn't judge her. Daniela in Sao Paulo rushes home to comfort her mother and she passes. Jada in New York despairs of the hatred all around even as she understands it, and she passes too. Young Kenta in Yokohama is still refusing to do his homework, but Progenitor doesn't judge children.
In between these we see the judgement on some superchars. Disguised as a reporter the Celestial asks the Mayor of New York Luke Cage how he rates his performance. The politician doges the question and so fails. As Thor fights Themex of the giant Eternals known as the Hex, Progenitor reads the inscription on Mjolnir and figures this means the Asgardian *must* be worthy of passing. He appears to Ms Marvel as her idol Captain Marvel and offers her and her family a chance to escape Earth with the elite of heroes. Kamala Khan knows this isn't what the real Carol Danvers would say and so passes. Charles Xavier is too busy psychically defending Krakoa when the judge appears as his son Legion and wants to talk to him, and so Prof X is condemned. Brandy Selby, the new young Starbrand, has her mettle tested against what seems to be a Dungeon God in a Dimension Of Shredded Tears. She does OK and passes. Dr Doom is offered a pass if he'll admit that Reed Richards is smarter than him. Doom laughs and passes himself. The judge agrees. Daredevil has violated his own moral code many times in the process of fighting evil. Progenitor appears as Christ to condemn him, and Matt Murdock accepts the judgement. He appears as Spider-Man (Peter Parker) to Spider-Man (Miles Morales) doing good at street-level. They exchange thumbs up.
And in between everything we sees Starfox touring the world to meet with the great and not-so-good. (His meeting in New York with Sebastian Shaw of the mutant Quiet Council was shown in Immortal X-Men #6.) He goes to Wakanda to confer with Black Panther. We see him in the Rose Garden of the White House. And at the end he addresses the United Nations to persuade them, without using his emotion-control power, to agree to his plan. If the world will agree to a package of universal human rights and environmental action then they can have access to more mutant tech, the secret tech of the Eternals and even that of the Celestials. They applaud him roundly. Afterwards Shaw approaches him and congratulates him on getting the mutants and 'good' Eternals to agree to it, but he questions whether he *really* speaks for all Eternals.
Then he returns to the bunker to discuss with Ajak, Mr Sinister, Sersi and Tony Stark what they can do about Druig, the current Prime Eternal. Ajak the Eternals' Priest still believes this is all just a test by her god and he won't really destroy the world. Iron Man and Mr Sinister want to launch an attack on him, but Sersi points out that non-Eternals can't get into the Eternals' hidden realms, at least not without someone sabotaging the Great Machine. Stark shows them footage of what Uranos and his sentient weapons did to Mars/Arakko (and the weapons are still there). Druig has Uranos locked up again in the Exclusion but he *could* let him do that Earth too. Starfox says Druig isn't desperate enough for that yet, but Sersi says he *will* be if he keeps losing. He only became Prime Eternal as a compromise, and the Uni-Mind can de-select him. She just hopes that Druig will make a mistake that will topple him before he can make the *big* mistake of letting Uranos out again.
Druig is consulting his confined 'grandfather' Uranos again, but still isn't ready to unleash *him*. He only has the remains of a day (but the Celestial hasn't judged *him* yet). His loyalists have sent messages suggesting he should send the Uni-Mind against the mutants again. This time including all Eternals even the Hex, which would enable him to use 1 of the Uni-Mind's warforms. So he sends out the mental summons, even to his opponents the 'good' Eternals.
We see the Uni-Mind approaching Krakoa in a menacing giant insectoid form. Mr Sinister has gone there to tell the mutants what's going on. Ajak, Kingo Sunen, Phastos, Sersi, Starfox and Thena join the combine, and Druig gloats that once he's used their power he'll use 1 of the Uni-Mind's functions to mind-wipe them. But Sersi lets him know that it was *they* who sent him this suggestion, and Eros calls for a vote on the Prime Eternal. Druig is still confidant his votes will outnumber theirs ...
... but then Sersi mentally contacts Ikaris and Gilgamesh who disable the Uni-Mind firewalls in the Great Machine, letting the X-Men and other mutants in. And they and the 'good' Eternals all vote overwhelmingly for Eros as Prime Eternal. (Well, his Titanian brother Thanos was PE before Druig.)
Now Druig knows he's going to lose so he orders the Machine to release Uranos so he can join the Uni-Mind and use his 'elder' status to take over so that he and Druig can rule together. But of course as soon as he's free Uranos just does what *he* wants to, which is to unleash weapons from the Eternals' armoury through portals all over Earth. And Druig realises he may have made a mistake. Uranos also seals the Machine even from access by other Eternals, and defeats the 2 who are inside it. So Sersi calls in their backup plan from Mars ...
... which Iron Man has organised. Uranos had previously used such portals to send his weapons to Mars. Now Tony Stark reopens 1 of *those* portals to send Magneto and Storm through from Arakko to Uranos in the armoury, and they blast him with their combined power. Then Stark gives them control of all of the portals which now all funnel blasts (from the Sun?) onto Uranos. But Magneto, who has been functioning without a heart (since Uranos ripped it out in X-Men Red #5), dies in Storm's arms. (And apparently he can't be resurrected because he deleted himself from the backup database as a political statement.)
In the aftermath Uranos is back in his cell. Ikaris and Sersi discuss making amends to the mutants. The Celestial chooses this moment to judge them, Ikaris yes, Sersi no. As the day of judgement nears its end Eros speaks to Progenitor about the deal he made and tells him they need more than this day to implement it. But their judge says that humanity won't change, and he's seen enough to know that they don't deserve to live. And he kills everyone? (So what's the next issue going to be about?)