As their civilization continually thrived due to their lack of ethics, the Prosilicans got greedy and sought to use the Watchers' technology to take over planets creating nuclear weapons and warfare, which caused an all-out war throughout the entire cosmos.
Spider-Man, the Avengers, the X-Men, the Champions, and the Fantastic Four help save civilians from the Moon rubble falling to Earth while dealing with the Badoon invasion.
The She-Hulk sees two TVA agents, Justice Peace and Justice Love, observing the chaos before disappearing while the Jack of Hearts gets confused about someone she was talking to, and the Silver Surfer, along with the Griever at the End of All Things, discovers an agonized Eternity (the living embodiment of the Marvel Universe) who was on his deathbed poisoned by the catastrophic cosmic war the Prosilicans orchestrated.
Meanwhile, Wrath, the Reckoning's leader, devises a plan to incite a cosmic war to take down Watchers as he sends the Badoon to Earth.
[9] In Raj-Lek, Wrath slaughters all the Recluses, including the Watcher Qyre as he taunts him for his eternal silence and non-interference while Reed Richards broadcasts a message to all the heroes on Earth to help them fight this invasion and contact the Silver Surfer.
After gazing at Eternity, the Surfer informs Reed and the team that the Prosilicans gave Watcher-level technology to lesser-known warlike conquerors, causing multiple invasions and chaos throughout the cosmos: the Badoon invading Earth, the Morani assaulting the Shi'ar Empire, the Mekkans laying waste to the Kree-Skrull Alliance, and the Annihilation Wave attacking the planet Spyre (home of the cosmic ray hosts known as the Unparalleled).
Reed, the Thing, the She-hulk, and the Jack of Hearts arrive in Shi'ar space to protect the M'kraan Crystal, but they are too late when they discover the army of Morani under the leadership of Rapture and Reject of the Reckoning invertedly defeated the Imperial Guard.
During the battle, Rapture gravely injures the Thing as she takes the crystal along with Reject, and the She-Hulk realizes why this is her fault after learning where they are heading.
Using the Ultimate Nullifier as a conduct, the Silver Surfer lures Destruction to confront the Reckoning as he departs Asgard to save Eternity.
Johnny Storm arrives on the planet Spyre and successfully defeats Annihilus by taking his control rod and his ships while sparing him.
[11] The Badoon, led by Ruin of the Reckoning, attack and storm the Baxter Building, in which Reed receives contact from Valeria and instructs her to initiate Protocol: Zero.
Johnny and the Unparalleled arrive at Anelle-vell, capital of the Kree-Skrull Empire, to provide aid for Wiccan and Emperor Hulking along with the Guardians of the Galaxy and the Starjammers to fend off against the Mekkan army.
[13] From the Baxter Building, it is revealed that Franklin, Valeria, Alicia, N'kalla, and Jo-Venn were unharmed and Protocol: Zero is meant as a failsafe to sabotage the Forever Gate, preventing Ruins from gaining access to it.
Ruins reveals to them that the Prosicilans' plan is not to destroy the universe, but to gain control of three existing Nexuses of Reality, including the M'kraan Crystal.
As Ruins departs with the remaining Badoon, Franklin and Valeria follow him right before the Forever Gate permanently shuts down, much to Alicia's concern.
Now fully armed with M'krann Crystal shards for his armor, Wrath and his army arrive at the Watchers' homebase to initiate the attack after killing the Watcher guard while Ikor (who is fully aware of the Prosilicans' invasion) refuses to delay the Cyclopedia Universum and sends Emnu to Dar-Kenda to check on "the Apex on All Reality".
Meanwhile, in the Barrens, the side-effect of the Cyclopedia Universum causes Reed's brain to begin to expand, transforming him into a Watcher-like being which allows him to bestow the Watchers' power and increased intelligence, learning that he has less than 10 hours from dying.
As Reed and Ben depart, the She-Hulk opposes this but Jack, however, chooses to remain stranded within the Barrens as he blasts her to the Forever Gate.
On Planet T-37X, the Reckoning encounters the Watcher as Wrath tosses the shard, releasing the Barrens' toxic gas on them as a reminder of his people's suffering.
Uatu understood this as he tries to reconnect with his people by revealing the truth of Emnu's actions and the Watchers' responsibilities while Fury stays to protect him.
Eternity, the Griever, and the Queen of Nevers congratulate Norrin Radd and Johnny Storm for their actions in saving the galaxy and confirm that the First War is finally over.
Uatu erases all the toxic Barrens from existence and invertedly recovers the destroyed nine-tenths of the universe, renaming it the Borderlands, which he describes as the Canvas of Infinite Possibility.
Uatu's action allows the Jack of Hearts to reunite with the She-Hulk right when the TVA agents arrive to ensure Galactus's resurrection.
With their tasks complete and the universe saved, Uatu sends everyone home to restore the damage the Prosilicans have done while the Fantastic Four go their separate ways: Johnny chooses to stay with the Unparalleled for the cure, Ben wishes to see his family from his departure, Reed and Susan return to the Forever Gate to check on their children, and Doom makes his farewell departure with Cormorant.
With his homebase restored, Uatu rebuilds a new Watchtower for Fury and entrusts him to secure the Ultimate Nullifier as the Unseen and humanity's shield.
[19] According to Comic Book Roundup, Reckoning War: Trial of the Watcher #1 received an average rating of 8.1 out of 10 based on eleven reviews.