Synopsis
When he was younger Kang The Conqueror heard of the massacre of the university planet Phearthon and wondered who did it. Now many years older it is his time-travelling self that leads his spacefaring army to raze the academic world in search of a particular alien scholar who knows all about the Missing Moment - 1 second of history that no time-traveller can access. The alien tells him that the Moment is the hidden start of the road to the greatest prize ever. He whispers (in alien) the secret of that prize but says Kang will be cursed by the knowledge because only heroes can overcome the necessary Tribulation Events, not a bloody-handed tyrant like him. So Kang kills him and orders his troops to search the place for all relevant documents.
1 personal year later on the flagship Prospero of his Tempest fleet Kang is bored. He's grown tired of his history of conquests which always ended in (temporary) defeat. He's begun to wonder if he's reached the limit of his conquering ability and begun to turn into his future self Immortus. The quest for the Missing Moment is all he has left to strive for. He summarises what he knows. The inaccessible Moment must be unlocked by a key (all metaphorically) forged by heroes overcoming Tribulation Events, and it is the 1st step toward achieving the Grail (again probably metaphorical). The TEs include:- The Death Moon. The Fall Of The Impossible City. The King Of Magic. The Cannibal Culture. He has scoured the future and found things that match these names. But how will become a hero that meets them?
Then someone materialises within Kang's private room. It is a hooded and fully-masked figure who declares that neither of them can fit *that* bill, but he will be the Conqueror's competition for the prize. Kang orders his room to kill the intruder but his defences don't activate. The other names himself Myrddin and says that he knows the Conqueror's security codes and has used them to disarm the room. Kang then orders his 'raiment' to activate as mask and armour and arm him with a sword. He scoffs at the other's name, saying he has met the real Merlin Ambrosius. Myrrdin parries the sword with his own (wooden?) staff and reminds his foe that heroes are needed for the TEs, and he has created his own band of knights, the Twilight Court.
Those heroes also meterialise. We see them and are told their names:- Artur the King, Mordred the Witch, Galehaut the God, Bercilak the Construct, Parsifal the Icon, Bedivere the Engineer and Lancelot the Star. Kang wonders if he has traitors in his army who have allowed his superior security to be breached. But now he recognises that his flagship is lost so he orders Prospero to self-destruct and his armour does an emergency timejump.
As he moves through time Kang sees images of events in Marvel's near future, but none of them are useful. Instead he heads for 1 of the TEs he scoped, the Fall Of The Impossible City. In particular he lands in Toronto whose buildings are being warped by the Citysmith. Galehaut follows him and attacks with her mighty fists. Kang scans her and recognises an Asgardian gene splice. He responds with Z-Beams which don't bother the God at all, but they are teleport markers which allow the Conqueror to send her away.
Lancelot follows, angry at what he might have done to her comrade. Kang now works out that they are both much younger than they seem - they've been artificially aged. She attacks with 2 energy blades emitted by her hands. He responds with real sword ported in by his raiment system, but 1 that scintillates with energy. They spar and Kang compliments her skill, but he declares he can use her heroic nature against her. He gets raiment to teleport in 6 fragmentation bombs and Lancelot rushes to save the surrounding civilians.
Kang timejumps again and see more fragments of 2023. His target this time is the Death Moon TE in the Sonoran Burn Zone. He finds Bedivere and Bercilak there waiting for him but they don't ambush him. Bedivere speaks because Bercilak never does. He tells Kang that he has no powers because he was the 1st created after the king. But instead he has the brains to create his own weapons. His armour extrudes a big gun which Kang generates a force field to repel. He recognises that the armour is based on Technarchy tech. He then turns to face Bercilak but he's ported to behind him, and his touch makes K's raiment system begin to breakdown. Bedivere says Bercilak is a nanohive entity whose computing power allowed it to fold space-time (to get through the force field and behind Kang) and launch a nanoware attack on his AI.
Bedivere now attacks with a sword which can split the forcefield. K gets a sword again to parry. They spar until K gets a different sword which pierces B's armour. He announces that it is the Ebony Blade created by Merlin and used in this era by the Black Knight, Dane Whitman. Kang found it 1,000 years later on a planet where its maddened owner had killed the rest of his people before committing suicide. He prepares to execute his foe but silent Bercilak cries "No" and causes K's armour to take him back into the timestream ...
... where the Conqueror sees more future visions before being delivered to Mordred the Witch-Knight in the Between-Time surrounded by Tarot cards. She doesn't intend to fight him. She is the Chaos Agent of the Twilight Court, which Kang interprets as that she might betray Myrrdin. She replies that Mordred was the Judas of Camelot and it is that story she was created to embody. Judas betrayed Christ but without him there would have been no resurrection. On the other hand Mordred betrayed Arthur and ended Camelot. But she must now work out what the effect of *her* betrayal would be. She knows Kang is a villain. He agrees but says so is Myrddin - they seek the Missing Moment for the same reasons. She decides to let Artor decide.
And so they all meet up at another TE, the Cannibal Culture in the Blue Area of the Moon. She tells her king she has brought Kang for judgement. Artor says K has already been found guilty of untold deaths across the universe. Mordred responds that they are knights, not executioners. Kang deserves a proper trial. Artor is compelled to agree but Parsifal offers to take on the accused in a trial by combat. Kang also agrees and removes his armour, so Parsifal dispenses with his weapons.
Kang is confidant of his martial skill but doesn't know what power his opponent has. Parsifal invites him to attack. K rains blows by fist and foot but P dodges them all while complimenting every 1. He explains that as long as his cause is just he cannot lose. K can't figure out what genetic power could do that, and without his AI he can't discover the answer. And obviously the knight's cause *is* just because K *has* killed millions. He plays for time by asking P why the king doesn't fight him. While they continue the bout the knight replies that it would be an unfair fight because Artor wears the Armour Of Chthon. He was the 1st from the Cauldron Of Rebirth but as the test case the result was flawed. His body is weak and needs the armour to sustain it. But his heart is the noblest of all because any lesser man would be immediately corrupted by the cursed armour.
Now Kang has found a weakness. He goads Parsifal by insulting the king. He says that Myrddin is not worthy of P's service, and neither is Artor. He's a puppet king, a weak failed experiment held together by a cursed armour. The knight retaliates in anger, and Artor calls out because he realises what K is doing. And in that moment P's cause is not just, and Kang is able to KO him with 1 punch.
Artor declares that Kang has won the trial, if by foul means. Kang takes the opportunity to repeat that Myrddin is as much a villain as himself. He's using them to kill him, and he'll use them as heroes to win through to the Missing Moment to gain a cosmic prize. At which point Myrddin appears to declare him a liar and stab him through the back of the chest with his staff. Artor protests that K had won the trial by combat. Myrddin says that he didn't deserve a trial. Kang swears to stop him getting the Missing Moment, and timejumps away.
He escapes to the blackness of null-time (a failsafe coded separately from his corrupted AI). More failsafes are trying to repair his body but they're merely succeeding in postponing his death. He needs help, and his own band of heroes.
In an epilogue in Myrddin's quarters we see him with a 'chessboard' with pieces representing Kang (tipped over), Dr Doom and Ultron. 2 more pieces have their backs to us which the Marvel Fandom Wiki identifies as Baron Mordo and Mr Sinister. He had hoped for a better showing from Kang, and wonders how he would have reacted if he knew who Myrddin really was. But he's not going to remove his mask until all the other pieces have been similarly dealt with.