Synopsis
Previously page:- The ghosts of T'Challa's Black Panther ancestors told him it was his duty to defend Wakanda (and hence the Earth and universe that contained it) no matter what it took (such as destroying the innocent world of the Great Society). Maximus made a slight breach in the stasis cube containing Thanos, Proxima Midnight and the bones of Corvus Glaive. The Illuminati left the anti-matter bomb they would use to destroy the GS's Earth at the incursion site on their own Earth - GS'er Dr Spectrum went to get it, pursued by Black Bolt. On the GS world Dr Strange revealed the evil power he had obtained to defeat the GS.
We begin with a flashback addendum to the meeting of BP spirits in #18. The ghost of T'Chaka, T'Challa's father, talks to his son privately. He asks why T'Challa hasn't yet killed Sub-Mariner for what he did to Wakanda in Avengers vs X-Men. T'Challa claims that he thinks Namor has a destiny that will be useful to Wakanda.
Now BP, Namor and Tony Stark without his Iron Man armour watch horrified as a ginormous tentacled monster summoned by Dr Strange last ish reaches from our Earth to the GS 1 and disintegrates the Great Society members. The boy who is The Norn is helpless without his magic artefacts. Speedster Boundless tries to shake herself free to no avail. Sun God tries to help The Rider, but it's no use. Even he is reduced to a dying husk. (Namor killed The Jovian last time.)
But now our trio of heroes are more worried about Dr Strange, who seems to be out of control. Panther and Stark rig up a weapon using 1 of the Iron Man gauntlets.
Back in the Wakandan Necropolis Maximus is telling the captive Black Swan what her problem is. He's been studying records of other Black Swan appearances the Illuminati have viewed through Reed Richards' space-time bridge. She and her sisters seem to have a typical game plan - she recruits heroes from an Earth (as seen in #15 at 1st to destroy other Earths to protect their own, but later to come with her after their own Earth goes). But this time she's made a mistake and recruited some kings (even though the Illuminati think BS is their prisoner, and they're doing things of their own free will).
The kings (Black Bolt, Black Panther and Sub-Mariner) are not like other men - they are used to taking big decisions and big responsibilities. (I'd guess some of the other Illuminati, Dr Strange for sure, are like that too.) So Black Swan has underestimated them. But Maximus adds that he could be a king too (he's taken his brother's throne before now). With the implication that he could be on BS's side.
While we hear Maximus' explanation, we see his brother Black Bolt chasing Dr Spectrum to the anti-matter bomb. They battle for it, but BB's shout is more than enough to strike down DS. Then he takes the bomb to GS's Earth.
When Black Bolt gets there he finds that the others have already rendered Dr Strange unconscious. Bruce Banner is still out of it too, but Beast and Mr Fantastic have woken up. They prime the bomb as Sun God painfully crawls towards them and begs them not to do it. They offer to take him with them to Marvel Earth, but he prefers to die with his world.
When the Illuminati get back home, Bruce and Strange have recovered too. They try to decide who will trigger the bomb. Reed Richards can't bring himself to do it, followed in quick succession by Tony Stark, Bruce Banner and Henry McCoy. Stephen Strange says he's already done enough. Black Bolt doesn't get a chance to (not) answer because T'Challa says he'll activate the trigger.
The spirits of his ancestors are there to watch him save Wakanda again. T'Chaka claims that Wakanda must be saved because it shows the way for humans to live (ecologically?) in the future. (This point is moot. If Panther doesn't destroy the other Earth then the whole universe will die, so there won't be a future humanity to learn from Wakanda's example.)
But T'Challa can't kill a whole world, no matter what the stakes. He's killed individual men for Wakanda. But killing a world is just wrong. So the other Panthers turn their backs on him and cast him out.
But then Namor picks up the trigger. He says that his personal morality and honour don't matter over saving the lives of everyone on Earth (and in fact saving the rest of both universes). So he pulls the trigger and the Grand Society's Earth explodes above them.