Avengers Forever begins with a desperate threat: Rick Jones, long‑time ally of the Avengers and bearer of the powerful “Destiny Force,” is targeted for assassination by the time‑lord Immortus. Immortus dispatches his servant Tempus to kill Rick in a chronal ambush. However, Kang the Conqueror intervenes, destroying Tempus and trying to hold back Immortus’s temporal army. The Kree Supreme Intelligence urges Rick to call for help, and together with Libra (an ex‑member of the Zodiac), Rick summons Avengers from different points in time: past, present, and future.

The Avengers who answer the call are a motley crew, each with strengths and flaws. Among them: a disillusioned Captain America, pulled from a moment when his faith in institutions is broken; Yellowjacket, mentally unstable and unaware of his identity as Hank Pym; Giant‑Man (also Pym) and the Wasp from the present; Hawkeye just after the Kree‑Skrull War; Songbird from the near future; and Captain Marvel from a more distant future. Each character contributes something unique—not just combat power, but emotional balance, moral conflict, and moments of doubt.

The story then plays out across shifting timelines and realities. The Avengers pursue Immortus through various eras—ranging from the American Old West, to alternate 1950s Avengers, to future dystopias threatened by alien invasions.  They learn that Immortus wields the Forever Crystal, a powerful artifact capable of manipulating many realities. Meanwhile, Kang reveals that Immortus serves the Time Keepers: beings who believe humanity may become such a cosmic threat that it must either be contained or destroyed.

As the stakes escalate, moral questions dominate: is it just to punish or erase entire futures based on what they might become? The Avengers reject the idea that humanity should be judged for possible futures, arguing for chances, for hope.  The final battles are massive and temporal in scope: corrupted Avengers from twisted timelines versus the true Avengers, interventions by Kang to prevent his own destiny, and the impending confrontation with the Time Keepers themselves.

In the end, the Time Keepers are defeated (including the killing of the future Immortus), Kang and Immortus are separated into distinct beings, and Rick Jones is gravely injured. To save him, Captain Marvel merges with Rick, which has lasting effects on his relationship with the Destiny Force. All the summoned Avengers return to their proper times, bearing the memory of what happened.  The story closes feeling like a tribute to Avengers history, with haunting “what ifs” but also firm reaffirmations of heroism, choice, and the value of hope even across time.