Synopsis
The previously page recaps the endings of #3 and Avengers #20. From Av#20 we see Captain America persuading the Galactic Council to surrender to the 1 Builder who remained on the Kree capital Hala after the Council drove the Builder fleet away. He proposes surrender because, despite their victory over Hala, they still can't defeat the Builders in open war. And in #3 Thanos came to deserted Attilan to demand his son from Black Bolt. And BB's response was to destroy Attilan with his voice.
Cap and Captain Marvel are attending a meeting of the remains of the Galactic Council (Annihilus, Brood queen, Gladiator [with Mentor] and Super-Skrull) when they hear that the Builder has agreed to meet with a representative to negotiate terms.
The Builder remote-confers with others. They agree to him accepting the surrender with minimal concessions. And they will stop jamming communications and broadcast the meeting throughout the galaxy. The Hala Builder arranges for all the important Kree to be present, including the Supreme Intelligence and Ronan's complete Accuser Corps.
In New Avengers #10 we learned that long ago many tribes of Inhumans split from the central group. And Thanos' half-Inhuman son was living with 1 of these tribes. Now we are told that this tribe is the Lor, their hidden city is called Orollan, and the young man's name is Thane, who works as a healer. (The tribe only has a small shard of Terrigen Crystal, and so only a very few people each generation are given powers via Terrigenesis.)
The ruins of the hovering city of Attilan have fallen on New York (mostly in the river, but still causing damage). Black Bolt's voice has also activated the Terrigen Bomb built by his brother Maximus. This affects all people in the world with any Inhuman DNA. There's presumably been a lot of interbreeding going on because we see apparently-normal people in the streets being transformed. Some people change immediately. It seems that others will remain in cocoons and emerge later.
Black Bolt and Thanos have both survived the fall of Attilan. They fight, as Thanos still wants to know where his son is. BB refuses to tell him, so Thanos appears to beat him to death.
In Olorran all the Inhumans are hit by the Terrigenesis Wave, including Thane who transforms immediately. The result is an explosion that kills all nearby Inhumans, and leaves Thane converted in form, with a blackened left hand that apparently caused the devastation.
Back on Hala Thor has been sent as negotiator. The Builder wants him to disarm. so he throws Mjolnir into space. The Builder agrees to spare the Council's worlds if Thor will abjectly surrender on their behalf. And the Kree and the Council (including J-son on Spartax) watch as Thor bends the knee.
But the Builder now adds that Earth itself and humanity will still be destroyed, for the sake of the universe.
Meanwhile Thor's hammer has flown through Hala's sun and now returns. In the conflict so far no Builder has been injured, just their robots and minions. But now Mjolnir smashes a large hole through the Builder's chest. As he dies the Builder tells Thor he's just caused the death of everything.
But the event is still being broadcast, and has shown the galaxy that the Builders aren't invulnerable. Thor makes a stirring speech, and Ronan and the Accusers pledge their support.