Hordes of good and bad versions of Avengers battle it out in the Citadel at the End of Time. The bad Avengers have been summoned thorugh time from alternate realities by the 3 Time-Keepers. The good Avengers have beem similarly brought here by 2 versions of Rick Jones using the Destiny Force. The Rick Jones's also use the power of the Destiny Force to enhance the good Avengers. Unfortunately the alternate future Jonz Rickard is doing the same for the evil Avengers.
The good Avengers are trying to stop the Time-Keepers from activating a chrono-cannon which will wipe out most timelines containing humanity. The Time-Keepers want to prevent humanity from overrunning the galaxy and beyond, and preserve the timelines that lead to their own creation at the end of time.
Meanwhile the Time-Keepers are also trying to evolve their enemy Kang into their pawn Immortus. They killed the actual Immortus last issue when he rebelled against them. Libra knows that the Cosmic Balance requires both Kang and Immortus to exist.
The older of the 2 Rick Joneses uses his Nega-Bands to swap back with the future Captain Marvel. Marvel has been trying to avoid something during this limited series, but now he is resigned to it.
Kang manages to halt his transformation into Immortus, and rejoins the fray.
Time-Keepers fire the chrono-cannon. But Rick Jones draws all the Destiny Force into himself (from evil Avengers as well as good ones?) and dives into the cannon as it fires, destroying it. Kang kills the Time-Keepers.
The destruction of the chrono-cannon leaves behind its power source the Forever Crystal. The Crystal is capable of destroying timelines, and creating others. Kang wants it, but Captain America picks it up. Cap is tempted by all the bad events in the past he could use it to put right. But he resists and destroys it.
At this point all the Avengers disappear except the original 7 brought from various times by Rick Jones in #1.
When Kang stopped becoming Immortus he actually split off a baby Immortus, who has now rapidly grown to an adult, but still much younger than the original. The new Immortus has the old Immortus's memories, which is strange because he has just been born from Kang. He says the Crystal isn't destroyed, just gone to Limbo to await its destiny.
Libra says that Kang and Immortus have been split into separate beings, as Immortus used the Forever Crystal to split the original Human Torch into 2 beings, as seen in #8, one of which could go on to become the Vision. Kang is no longer bound by his fate to become Immortus. The new Immortus leaves to follow his own fate. Kang goes too.
Rick Jones is dying due to the explosion of the chrono-cannon. Future Captain Marvel accepts his fate, says goodbye to his future love Songbird, and persuades the Kree Intelligence Supreme to help him merge with Rick, as the original Captain Marvel once did.
Libra sends Avengers, Rick and Supremor back to their lives. The Avengers from the past won't remember what happened. Yellowjacket returns to his wedding to Wasp in Avengers #60, Hawkeye to Hercules and his phone call home in Avengers #99, Captain America to the death of Number One of the Secret Empire in Captain America #175. Those from the present and future will remember to some extent. Songbird returns to the future. Rick Jones, Giant-Man and Wasp return to the present between Avengers v3 #11 and 13.
Rick Jones discovers he can swap places with Captain Marvel via the Nega-Bands. But the Captain Marvel he swaps with is the younger then-current version. However this version suddenly takes on the hairstyle, skin colour and costume of the future version, and gains his father's cosmic awareness.
Meanwhile Libra leaves the Kree Supremor back in the Blue Area of the Moon. But after he has gone, Supremor calls the Forever Crystal to him.