The Watcher explains his position as the observer and recorder of the history of Earth, which includes its deviating realities. He mentions one recurring anomaly in particular, that of a young mutant named Legion who timetravels into the past to eliminate his father’s greatest enemy, Magneto. Most times, Xavier, his father, is killed defending Magneto, which throws the planet into what is known as the Age of Apocalypse. Instead, the Watcher wants to show what happened to one of his watches when both Xavier and Magneto were killed.
Thousands of people died when Legion went back in time on this Earth. Instantly, humanity was frightened of the powers mutants held. Governments began placing mutants in concentration camps. Non-mutant superheroes came into existence and helped safeguard the world. The Savage Land, under the watchful eye of Ka-Zar, became a refuge for mutants. Eventually Apocalypse was able to amass an army of mutants, bitter at the prejudices they faced. They swept through like a tidal wave leaving few to oppose them. Apocalypse set up facilities to begin culling humans. Mutants and superhumans either subjugated themselves or were exterminated.
Decades later, the unmolested Savage Land had prospered. The mutants there were peaceful. Some worried that Apocalypse’s eye would one day turn toward them; Scott and Jean Summers were two in particular. They spent much time training their son to be prepared.
Amid a telekinetic display that outshone his mom, the time for Nate had come. Jean sensed the attack moments before it happened. Scott had enough time to ask what was wrong before seven of Apocalypse’s soldiers arrived for the slaughter. Holocaust led the charge, with the orders no one be left alive. Jean ordered Sauron to extract Nathan to safety. Despite his desire to stay and fight, Jean would not allow it. She knew his life was too valuable to die on that day. An instant later both Scott and Jean were vaporized by the Banshee’s sonic scream. All of Nate’s emotions vanished. The void filled by rage.
Sauron took Nate as far into the surrounding Antarctic as he could. They crash landed, Sauron too weak, or too hurt to move. Nate sensed someone nearby and prepared to fight. He dove at the man, threatening to kill him and Apocalypse. The man pinned Nate and stuck his fist up to his chin. Claws popped out on both the left and right side of his head. The stranger warned him there was yet a third claw. Logan got up and extended his hand to Nate. He assured the young man he was no friend of Apocalypse. In fact, the man that sent Logan to find him thought Nate might be their last hope.
It took months, but the group finally made their way to New York, to friends. While there Nate relayed the horrors of what happened at the Savage Land. Brother Voodoo, Sorcerer Supreme, informed Nate the world they lived on shouldn’t exist, that there was a time traveler who killed a man that would have prevented the rule of Apocalypse. He further explained that Stephen Strange, the former Sorcerer Supreme, who died in the process, uncovered this information. Before his last breath he forbade anyone from traveling back in time to rectify things.
Voodoo acknowledged to Nate the wisdom in that decision, the dangers too great, and told him their group was focused on saving the world by destroying Apocalypse. Captain America finished the discussion, explaining Strange’s belief that Nate was the key to their hope. Cap placed his hand on Nate’s shoulder and told him they were humanity’s last chance of stopping Apocalypse. Nate was honest about his lack of love for the humans, but agreed he’d do whatever it took to end Apocalypse.
After months of training under Captain America the small group of heroes became a force to be reckoned with. One night they took on three of Apocalypse’s scouts, two of which were Lady Deathstrike and the Absorbing Man. Captain America and the Thing led the charge, getting the drop on their targets. The rest of the group arrived for support. One member was rather reluctant, but Nate took care of that, giving the Molecule Man a psionic nudge that freed him from his reluctance to fight. From a nearby rooftop where Nate and Owen stood, a torrent of energy came pouring down that fried the bad guys where they had stood.
Captain America was not pleased with their actions. Nate explained how he had unlocked Owen’s ability to manipulate organic matter. That Owen transformed their flesh into water, which he in turn heated until it evaporated. Cap was still not pleased as he felt the situation was under control and the killings needless. Logan sided with Nate.
Brother Voodoo wanted the dissension to stop as the assault on Apocalypse was planned for the next day. Nate again questioned why Voodoo wouldn’t open a portal directly to Apocalypse’s chamber. Voodoo explained it would be used as a last resort as the realm of Dormammu was riddled with dangers more powerful. Nate asked him to use the Eye of Agamotto to guide him to the anomaly so he could prevent it from ever happening. Voodoo admitted his struggles with the decision, but was firm they follow the advice of Strange.
The next evening, the Defenders make their way to the stronghold of Apocalypse. They approach cautiously, Colossus remarks on how large it’s grown recently. He starts thinking of how things would’ve gone if they tried the assault a year ago. Logan shuts him down and tells him to focus.
Nate grabs Owen’s shoulder and asks if he’s ok. Owen admits he’s a bit apprehensive. Nate tells him not to be so doubtful. Thing passes by a sign reading “Yancy St.” He reminisces about the Fantastic Four’s choice to become Apocalypse’s four Horsemen, their decision resulting in their deaths. Cap assures him they’re in a better place.
Logan sniffs something and tells them to halt. He can’t quite place the smell, but it’s familiar. Black goop starts crawling up his boots. Brian Braddock, inside his Iron Man suit, goes topside and finds a lot more of the black gunk strung about Apocalypse’s citadel. He’s ordered back down, but is suddenly surrounded by dozens of Spider-Man clones. Logan asks Cap’s stand on killing clones. He authorizes lethal force.
The Defenders go to town obliterating the Spideys. Unfortunately, Holocaust emerges from the tower. Brother Voodoo attempts to keep him at bay so Nate can get inside his head. Nate explains he can’t bust through, that Holocaust’s mind is fortified. He yells for Owen.
Holocaust lashes out at Voodoo sending him flying. Cap runs up and strikes him with Mjolnir. Now Holocaust goes flying back. Nate runs over to Voodoo and grabs him by the collar. He demands Voodoo open the entrance to Dormammu’s realm. Voodoo remains adamant against it.
Braddock goes after Holocaust and begins blasting away. He is soon caught up in half a dozen web lines. Holocaust is mere seconds from dealing a mortal blow when Thing comes up and reminds him he’s standing on Yancy Street. For the second time Holocaust is sent flying back, courtesy of Thing’s punch. Pieces of his armor break free, much to his disbelief. Thing approaches Holocaust and reminds him that he killed his family and took his arm. His only regret is that Holocaust won’t see the clobberin’ that he gives his father.
Down below Colossus picks up Logan and throws him in Braddock’s direction. Logan slices through the weblines holding Braddock in place, making the fastball special a rousing success.
Nearby, Cap takes out some more clones with some summoned lightning. He urges his teammates to finish the battle.
Holocaust gets up and grabs hold of Thing’s bionic arm. He tells him he doesn’t even remember killing his family, that their lives were insignificant. Cap orders Sauron to grab Thing and get him out of there. Cap yells to Ben they need to go, but Ben doesn’t want to leave just yet. Just as Sauron arrives to grab Thing Holocaust fries them both. Cap yells out in astonished horror. Colossus charges off in a murderous rage and receives the same treatment as his two fallen teammates.
Nate urges Voodoo to open the portal; they’re losing. Voodoo complies this time and the six remaining Defenders enter, Cap only after Logan knocks him through.
Inside, Brother Voodoo begins an incantation to take them straight to Apocalypse’s chamber. He asks Nate to scan it and make sure it goes to the right place. Nate checks it and confirms. Just as things couldn’t get much worse, Dormammu shows up. He remarks on the sorry reality they must come from if Jericho Drumm is the Sorcerer Supreme.
Cap throws Mjolnir at Dormammu, which he easily deflects. Voodoo orders everyone through the portal and insists he will restrain the demon. Mjolnir flies back to Cap who tells Voodoo they’re not leaving. Voodoo assures him they will all die then. Cap still refuses to run so Braddock flies by and grabs him. He tells Cap they have no choice.
Nate telekinetically throws Owen through the portal. He alone now remains behind with Voodoo. Dormammu begins wrapping Voodoo up in some wispy green energy. Voodoo begins a counter-chant, but is betrayed. Nate summons the Eye of Agamotto to him. He apologizes to Voodoo and leaves. Voodoo is swallowed up in the green energy; his last audible cry is “Nathan”.
Nate exits the portal and finds himself in the temple of Apocalypse. The four Horsemen are poised to strike. Cap shouts out a motivational war cry and the battle begins. The Juggernaut strikes first with a powerful charge. He comes barreling head first at Rogers. He strikes Juggs with Mjolnir and rips the helmet from his head. He lifts said helmet from the fallen Horseman and tells the Defenders, “No Mercy!”
Braddock tells his teammates to focus on the Hulk. Both he and Rogers attack. The Sub-Mariner sucker punches Logan as his focus is on the Hulk too. He begins to rationalize that he would fight for the devil himself if it would keep Atlantis free. Logan responds by jamming his claws through his neck and out his eye sockets. His victory is short-lived as Storm fires lightning at him, taking him out of the fight for a bit.
The fight with Hulk is pretty much a stand-still as Braddock and Rogers throw everything they have at him. Nate grabs Owen by the arm and tells him they’re going after Apocalypse. Cap yells to Owen they need his help. Distracted, Cap is knocked aside by the Hulk who also snags Braddock’s leg. He pulls him down and rips off one of his arms.
Nate and Owen find themselves face to face with Apocalypse. Apocalypse tells Nate he knew of the Summers’ potential and asks him to take a position at his side. Nate scoffs at the idea and introduces Apocalypse to Owen. Nate enters Owen’s mind and pushes him to his maximum potential. Apocalypse disintegrates from within his armor.
Outside the chamber Logan and Cap survey the scene; the four Horsemen are dead as well as Brian Braddock. Cap rushes off to check on Nate. He enters and is shocked to find him clad in Apocalypse’s armor, Owen’s skeletal remains nearby. The Eye is floating near him. He tells Cap to get out of his way, that this is their chance to make things right, to bring back everyone who was killed.
He explains he made Owen open a portal to the moment Xavier was killed. With Apocalypse’s armor he will be protected as he goes back in time to fix it. Cap charges up Mjolnir. He tells Nate he won’t let him do it. Nate yells at him as the portal begins sucking in Mjolnir’s energy.
Nate pleads with him, that he can stop it and bring about a golden age. Cap tells him the world doesn’t need another tyrant. Cap blasts lightning through Nate, destroying him.
Logan enters and wants to know what happened. Cap stares emotionless and responds, plain and simple he thought the ends justified the means. Logan asks if he’s referring to Nate or Apocalypse. Cap tells him both. With the portal still open Logan asks if they’re just going to stand there and let it close. Cap tells him that’s exactly what they’re going to do.
The Watcher explains that by using the Eye of Agamotto and Owen Reece, Nate did open a portal back in time, however it was to the past of another reality. The lighting intended for Nate also passed through the portal killing thousands, which brought about the same events at the beginning of this reality.
The result of Nate’s actions created a domino effect. Countless worlds lost both Xavier and Magnus. Uatu remarks that it is always best to try and better the situation than to try and undo what has already happened. Unfortunately he can’t impart this wisdom on anyone, “...for it is my charge only to watch...”