Synopsis
This issue starts in the middle of something before flashing back to show us what's going on.
Captain America is in a jungle preparing for conflict by sparring with a tree and reminding himself that he must never take winning for granted. We see that his fist has an orange glow and he's punching holes in the trunk. The view pulls back to show very large animal bones. Then Dr Doom wreathed in flames attacks him, talking about winning the round. And we are informed that this is the Savage Land, venue for the 1st round in the battle for the Phoenix Force.
The Phoenix Force has given each of the contestants a small part of its power. Victor Von Doom calls out to it to abandon the contest and give *him* its full power. Together they can burn down the cosmos. Steve Rogers is convinced that he can't let that happen, but is also worried about what he would do if he himself won. He remembers how the Force corrupted its users before (as in the Avengers Vs X-Men event on its last visit). He hurls his shield now also flaming, and stands up encased in a red and gold armoured costume sporting the Phoenix symbol.
Now we get the flashback to Avengers Mountain HQ and the Phoenix Force 'nesting' in a nearby now-active volcano surrounded by Wakandan helicarriers. Black Panther attaches a huge comms wire to the back of his costumed head which connects him to the dead body of the Celestial that the Avengers use as their base. They daren't use telepaths to contact the Phoenix for fear of takeover so T'Challa is going to 'talk' to it using the Celestial's brain. The other Avengers (Blade, Captain America, Captain Marvel, Ghost Rider (Robbie Reyes), Iron Man, She-Hulk and Thor) along with Okoye watch from a 'carrier.
But Panther hardly has time to ask the Phoenix why she's here before Sub-Mariner rises up out of the Arctic Ocean and pulls the plug from his head to declare that the Phoenix has come for *him*. He called to her (#32) and now she is here to be reunited with him (he was 1 of the possessors of the Phoenix Force in Av Vs XM). He tells his Defenders Of The Deep (Andromeda, Bloodtide, Echidna, King Crab, Orka, Tiger Shark and a tentacled beast who I don't think is ex-member Manowar) to keep the Avengers at bay while he goes to join the Force and turn the surface world into a flaming hell.
But Wolverine is there to stop him.
Back in the present the empowered Cap is beating Doom hands down. But then he remembers the seductive lure of the Cosmic Cube and the Infinity Gauntlet, and is suddenly afraid of what he's becoming. The Phoenix wants the heroes to kill each other and the last man standing wins the prize, but Steve doesn't want to play that game. This of course allow DrD to turn the tables.
Earlier we see Avengers vs Defenders (Black Panther vs Tiger Shark, Blade vs Bloodtide, Captain Marvel vs Echidna, Iron Man vs the tentacled monster, Okoye vs Andromeda, She-Hulk vs King Crab, Thor vs Orca) while Captain America helps Wolverine subdue Namor. Cap reminds Logan that he fought *with* the Avengers during Av Vs XM, and Wolvie assures him the X-Men won't oppose the Avengers this time.
Present-Cap remembers feeling a voice of fire in his head as the Phoenix rose from its next. It called to him as Steven, the man who couldn't die by ice (obviously a reference to his suspended animation since WWII). And he knows that others felt similar calls. At the time we see BP, Cap, Shulk, Subbie and Wolvie wreathed in flame, and then they disappear. Steve remembers them being taken up into the Phoenix and transported to the Savage Land.
Now Doom thinks he's killed Cap and demands that the Phoenix Force chooses *him*. But Captain America rises again until Doom blasts his armour off leaving what looks like the pre-Super Soldier Steve Rogers. But the 98-pound weakling still has the Phoenix Force to attack with. And then the Force restores him to his armoured Super Soldier state, and Doom realises the Force won't let Cap die because his indomitable spirit makes him worthy. Victor declares that if losing to a superior foe is a criterion then he resigns from the game. And the Phoenix lets him go.
Then she returns Captain America to join other candidates in a white space where he's greeted by Panther, Wolverine and She-Hulk in her Jennifer Walters form. Cap confirms he won the bout and the view pulls back to reveal the other contestants. As well as Namor there are American Eagle, Black Knight, Echo, Luke Cage, Man-Thing, Moon Girl & Devil Dinosaur, Orb, Red Widow, Shang-Chi, Shanna The She-Devil (and Zabu), Valkyrie (Jane Foster) plus Hyperion and Nighthawk of the current Squadron Supreme. And Howard The Duck!