Synopsis
The previously page shows the Builders destroying the Galactic Council's Behemoth Ringworld; Black Bolt reporting to the Illuminati that Thanos wants the Inhumans to kill all their children of age 16-22, purely to ensure the death of Thanos' own son; Thanos telling his generals that he's going to extract this Tribute himself.
The comic then starts with effectively another previously page showing 1 bunch of Avengers on Behemoth after the Council's defeat in the Corridor, standing beside Kree, Shi'ar, Skrulls and Spartoi. Then high-speed Builder drone ships smashed into the Ringworld.
The Builders show recordings of the destruction to other races they encounter. Many like the Centaurians, Kree and Kymelians surrender.
Parts of Behemoth survive, and we find recognisable faces Captain America, Ex Nihilo and Thor with Annihilus of the Negative Zone, the Brood queen, Gladiator of Shi'ar, J-son of Spartax, Ronan the Kree Accuser and Super-Skrull. The Supreme Intelligence recalls Ronan and the Kree to their capital Hala. J-son suggests everyone else return home too, to defend their homeworlds. Gladiator and Super-Skrull say their forces will stay and fight.
Before J-son leaves he tells Cap that the missing Avengers (Captain Marvel's crew) are prisoners of the Builders. He won't say how he knows, but Annihilus senses betrayal. (We know that J-son tried to make a deal with the Builders in Avengers #19, and that's how they found the Ringworld.)
Cap says he has a plan that will require some bait.
Next day some Builders are accepting Ronan's surrender in orbit around Hala when they detect a fleet of ships approaching. All the Builder warships except the command ship and the huge planet killers move to oppose them.
But this is a feint as a small group including Mentor, Oracle and Starbolt of the Shi'ar Imperial Guard, Smasher the joint Guard/Avenger, and Bruce Banner and Falcon break into 1 of the planet killers. Mentor takes over the ship's controls and starts firing on the other planet killers, destroying 2 of them.
Unfortunately Banner turns into Hulk and accidentally breaks the controls. Fortunately there's a 2nd team invading another planet killer. Super-Skrull and Thor have taken it, and they too fire on other ships.
The Builders have lost 8 planet killers, and their command ship is crippled. They teleport to safety (presumably to another ship) and most of the Builder fleet jumps away, leaving the Gardener Ex Nihila on a suicide mission to scuttle the command ship. Some of the Builder ships stay to continue the battle.
Meanwhile another team of Avengers (Black Widow, Manifold, Shang-Chi and Spider-Woman) have rescued the captured Avengers (Abyss, Cannonball, Captain Marvel, Hawkeye, Nightmask, Starbrand, Sunspot and the comatose Captain Universe still in her stasis tube) as seen in CM#16 (and the upcoming Avengers Assemble #19).
Black Widow convinces Starbrand to destroy the remaining Builder warships.
Back on Earth we get a glimpse of Red Hulk facing Supergiant (probably from next month's Thunderbolts #16), Luke Cage leading Spectrum, Spider-Hero, Spider-Man and White Tiger against Proxima Midnight (from Mighty Avengers #1), and the Illuminati investigating another incursion (in New Avengers #10).
Then Thanos personally goes to Attilan where he finds Black Bolt alone in the throne room. Deep in the city the last of the other Inhumans are escaping through the Mouth of Eldrac. Maximus remains behind with Lockjaw the teleporting dog, and the device he built for BB in NAv#7-8. He arms the device.
Thanos has come for the head of his son, or he will destroy Attilan. But BB's answer is a shout which activates Maximus' device (as Lockjaw teleports Maximus to safety), and destroys Attilan anyway.