Synopsis
Captain Marvel (Genis-Vell) and Wasp have just escaped in one of Kang's chronospheres from the alternate timeline of the 1950's Avengers as it was destroyed by Immortus. Captain America and Giant-Man are in an alternate future war against 'Martians'. Hawkeye, Songbird and Yellowjacket are stuck in 1873 Tombstone in the main Marvel timeline. These seven Avengers have been plucked from various times to protect Rick Jones from Immortus.
Rick is safely hidden outside of time in Kang's time-Sphinx, monitoring the situation and keeping in touch with the 3 teams. Captain Marvel and Wasp's escape from the collapsing timeline triggers a cascade of images of Immortus on the Sphinx's viewscreens.
Captain America and Giant-Man have just helped the last remaining Avengers (Black Panther, Crimson Dynamo, Jocasta, Killraven, Living Lightning and Thundra) drive the 'Martians' off Earth (although it seemed a rather localised battle last issue). They now want to pursue them to their nests on Mars. The only usable space technology left on Earth is to construct spaceships from the remains of Wakanda's vibranium mound.
The synthezoid Jocasta is pregnant (the father is the now-dead Machine Man). It turns out that her baby needs the presence of vibranium for a successful birth. They also meet Mourning Prey and her insectoid children who need the vibranium to survive. From Mourning Prey's description we understand that Immortus had a hand in her situation. And one of the images Rick sees is of Immortus marrying Jocasta and Machine Man.
Captain America persuades Black Panther to use the vibranium to support life rather than pursue death for the 'Martians'. Then he and Giant-Man leave in their chronosphere.
Hawkeye, Songbird and Yellowjacket have lost their chronosphere, but they have found some Space Phantoms impersonating Western heroes. They are on the periphery of the buildup to a known Avengers adventure helping real Western heroes Kid Colt, Night Rider, Rawhide Kid, Ringo Kid and Two-Gun Kid against Kang. Because our Avengers know the other Avengers will win, they just want to avoid messing with the timestream and find a way home.
Songbird leads Hawkeye and Yellowjacket into Kang's revealed citadel and finds them a chronosphere. But Yellowjacket is suspicious of Songbird's too-detailed knowledge of the citadel. It turns out she is another Space Phantom (since partway through this issue), and when he drops his disguise the real Songbird returns from Limbo. It appears the Space Phantom was going to take them to Immortus, but instead they use the chronosphere to return to the Sphinx.
Meanwhile in the Sphinx Rick has recorded the images of Immortus. One of them shows him openly carrying the Forever Crystal which he constructed in #3 from Kang's city Chronopolis, and which now allows him to destroy timelines. It is unclear whether the other images are also of Immortus in his current state, but they may in any case show him carrying out part of an overall plan.
They show him officiating at the aforementioned marriage of Jocasta and Machine Man, but also at the joint marriages of Scarlet Witch/Vision and Cotati Swordsman/Mantis in Giant-Size Avengers #4. He is seen in Thor #282 where Thor sacrificed the time-travel capability of his hammer to save the planet of the Space Phantom. But he is also seen in places where he was not known to be:- at the meeting of Dr Doom and Rama-Tut in Fantastic Four Annual #2, and when Vance Astro of the Guardians of the Galaxy met his teen self in Marvel Two-In-One #69. There is also a meeting with the Badoon ruler, and a meeting with a Space Phantom and the Grim Reaper from around Avengers #107 when they erased the world's memory of Captain America's identity as Steve Rogers. And a mysterious image with Immortus, the Forever Crystal, a Human Torch and a body.
The Avengers decide to take the fight to Immortus in Limbo. But Rick Jones is worried, as is Captain Marvel who seems to know more about what is going to happen than the others do.