Synopsis
This issue begins with a flashforward of Colossus beating up someone who won't give in. It won't be a big spoiler to tell you that the cover suggests correctly who that is.
In K'un Lun Spider-Man is continuing the training of Hope Summers as seen in New Avengers #27. (Currently that involves standing on one foot on the pinnacle of a pagoda-like building while balancing 2 buckets of water suspended from a yoke.)
Some Avengers return through a portal from one of many missions to Earth, usually looking for teammates who have been captured by the X-Men. This time it's Captain America and Iron Fist plus She-Hulk and Wolverine supporting a wounded Red Hulk (presumably suffering from more than the metal cast holding the broken arm from last issue). And they've lost another member (Thor!) to the combined might of Colossus and Magik.
The situation is dire. Since the remaining Phoenix 4 (Colossus, Cyclops, Emma Frost and Magik) absorbed Sub-Mariner's Phoenix fragment last issue they have become even more powerful. Iron Man is lost in research (and looking like he might be lost in the bottle too) trying to find a solution within the connections between the Phoenix Force, the Iron Fist, Scarlet Witch's hex magic and Hope. And lots of Avengers are injured or captives. And Black Panther stayed behind in Wakanda trying to clear up the mess Namor's attack left last issue.
When Red Hulk is taken to the infirmary we see Captain Britain, Daredevil (probably), Giant-Man, Mockingbird and Scarlet Witch on the sick list. This agrees with the list of casualties on the splash page, except that I don't see Vision, and he's certainly not the extra bed-ridden character who looks like Black Widow (but we'll find her in the X-Men's prison later). The splash page also says Beast is injured, but he's certainly playing doctor here.
Hope is fed up of training and wants to go into action. Spidey gives her a pep talk, telling her that all this never-ending training will come in useful one day. Many of the other Avengers may seem like powerhouses, but in his experience there's always a time for the least among them to save the day.
Meanwhile Storm is watching with Armor, Gambit and Pixie (and with disgust) as Magik disposes of Thor in the Russian volcano that houses the extension of Limbo that she is using as a prison (as seen in X-Men: Legends #270). Many X-Men have abandoned the support of the Phoenix 4 as the Phoenix Force continues to corrupt them. Storm advises her companions to do the same.
Cyclops finds Emma Frost in the middle of a desolate desert, to get away from all the minds she can now read. She tells Scott she has found out from Avengers' minds that Hope is in K'un Lun, wherever that is. She also tells him she could end the conflict now by just switching all the Avengers' minds off. And she is afraid that part of her wants to do it.
Later she visits a man who she can tell once killed a mutant. No-one knew about it, but now Emma kills him in front of his family.
Storm visits her husband Black Panther in Wakanda and offers to help him and the Avengers. She says she wasn't party to the attack on Wakanda. She only sided with her fellow X-Men hoping to keep them under control, but now she knows that's hopeless. But angry Panther tells her to go. As High Priest of the Panther Clan he has annulled their marriage.
But T'Challa does take her message to the Avengers, and he, Captain America, Dr Strange, Iron Fist, She-Hulk, Spider-Man and Wolverine meet up with Storm and Prof X in the Limbo prison. Strange's invisibility spell gets them past the demonic guards, and they find the prisoners (Black Widow, Hawkeye, Luke Cage, Ms Marvel, Quicksilver, Spider-Woman, Thing and Thor) hanging from the ceiling in cocoons, as lamprey-like demons feed on their souls. They can't open a portal to K'un Lun from here, and Strange can't use his teleportation spells. So they prepare to carry the victims out.
But Magik senses them from the Bering Strait, where she is viewing her brother Colossus's experiment giving legs to whales. And she transports them both to slaughter the Avengers.
Spider-Man sees powerful Avengers being no match for the Phoenix 2, and remembers what he said to Hope. He uses his web-lines to hurl his compatriots towards the exit, and then brings the ceiling down to separate them from Colossus and Magik. Then he turns to hold off the Rasputin siblings for as long as he can.
Spidey is easily beaten by the powerful duo. But every time they turn their attention to unblocking the exit, he taunts them back into fighting him again. And as the flashforward showed, he just refuses to lie down. Magik chides her brother for holding back and not just killing him outright. They fall to bickering which Spidey encourages, reminding them that if one of them was to be thoroughly defeated like Sub-Mariner last issue the whole Phoenix power would be shared out amongst the remaining 3.
Meanwhile the Avengers have fought their way back out through the demons, and transported the captives to K'un Lun. Cap, Panther, Storm and Wolverine return to rescue Spider-Man, and find him battered but the only one still standing. Colossus and Magik have taken each other down and the Phoenix Force has left them.
Then the even-more-powerful Cyclops breaks through the dimensional barriers to K'un Lun, coming for Hope.