Synopsis
The Multiversal Masters Of Evil led by Doom Supreme aided by Mephisto conquered many alternate timelines. Avenger Prime (an alternate Loki) gathered an army of alternate Avengers in the God Quarry to oppose them. The Earth-616 Avengers and their 1M BC predecessors combined to defeat the MMOE while the Red Council of alternate Mephistos attacked the multiversal Avengers in the God Quarry. The Council were defeated but Mephisto-616 has absorbed them all to become 1 giant-size Mephisto. Doom Supreme led an army of multiversal Dr Dooms, including Doom The Living Planet, against the multiversal Avengers. Our Avengers and the survivors of the 1M BC Avengers joined the battle in the God Quarry, as did Galactus and the dead Celestial who is Avengers Mountain HQ (in Avengers #66).
The voiceover for this issue is provided by the Deathlok whose consciousness now animates the Celestial. (Avenger Prime also had an army of Deathloks but this is the last survivor of *them*.)
Galactus the World Devourer is eating Planet Doom, and the other Dooms are in a frenzy. The Goddesses Of Thunder combine forces with Thor of the Earth 616 Avengers, Odin of the prehistoric Avengers and Thor, God Of Fists to unleash a storm of lightning and Mjolnirs. Our Captain America and Captain Marvel join the Carol Corps and the Howling Commandos of alternate Steve Rogers, at least 1 wielding another Mjolnir. Old Man Phoenix (Logan) fights beside Ka-Zar, the latest Herald of Galactus to have the Power Cosmic. The 1M BC caveman Moon Knight is there with Mariama Spector, the Moon Knight of Earth-818, and the 818 Vision. Our Sub-Mariner uses his fists alongside the magics of Avenger Prime and Agamotto of the 1M BC Av. Our Iron Man, Nighthawk and Phoenix (Maya Lopez) fight Dooms with the 1M BC Iron Fist. Like all the others Valkyrie echoes "Avengers Assemble" with Ant-Man (Tony Stark-818), Star Panther and the Steve Rogers who is Weapon America. Gorilla-Man and Ursa Major fight Dooms to seek redemption for past sins. Meanwhile the Deathlok Celestial fires an extremely big gun at giant Mephisto, blasting his guts open. Mephisto shows how hard he is by eating his own innards and charging his foe.
Loki has Doom Supreme in mystic chains and Namor wants to beat him up. But the sorcerer Doom breaks free and tells them that their efforts are for nothing because the conflict has cracked the floor of the God Quarry and the power beneath it is breaking out. This power has now attracted Dark Phoenix, another survivor of the MMOE. But she is more concerned with vengeance against Doom for abandoning her. She threatens to tear out his lying tongue. So he removes his mask and kisses her to give her the chance, but responds to his kiss.
The Earth-616 heroes Starbrand (Brandy Selby) and Ghost Rider/All-Rider (Robbie Reyes) sit at the base of the ruined Avengers Tower and watch the carnage. Brandy has been rapidly aged from a baby to an old woman by the use of the Starbrand power, and using it again will kill her. In #11 GR/AR seemed to use up all his power trying to destroy the MMOE. But now Robbie says the power is still within him but as he evolved from GR to the mythical AR there seemed to be less and less of Robbie Reyes left. He fears that if he becomes All-Rider again he himself will disappear. But they believe that like all the legacy powers (eg Black Panther, Iron Fist and Moon Knight) their presence is necessary for victory to be achieved. So they decide to step up to the plate, starting with incinerating a bunch of Dooms.
Old Man Phoenix realises that the whole point of this war was to break open the God Quarry. Maya-Phoenix senses another Phoenix nearby. Dark Phoenix declares her intent to kill them both and Thor-616. But Lady Phoenix (who we saw in Av#63 approaching Earth-616 in 1M BC) has followed them all through time and the multiverse and now blasts DP to protect her 'son'. The Thunder God is now completely reconciled to the part she played in his birth, and they join Mjolnir with Phoenix Fire against Dark Phoenix.
Now Mephisto pauses in his hand to hand combat with the Celestial as he sees what lies below start to leak through the God Quarry ground. (I don't know if the panels on this page are supposed to indicate that Mjolnir + Phoenix Fire punched Dark Phoenix through the floor of the Quarry and caused the final breach.) He reaches out to a drop of it and becomes even larger and more monstrous. He looms over Galactus and the dead/dying Doom Planet and smashes his fists down on that DP causing a big hole in the Quarry floor.
The voiceover says that the Quarry is a dam holding back Entropy (which Old Man Phoenix calls the remains of an ancient multiverse) and that Mephisto's plan was never to rewrite the multiverse but to destroy it.