Within the multiverse, there exists a special kind of cosmic correspondence known as a "potential future."
For instance, the Wasteland Universe and Earth-2099 are both potential futures of Earth-616. As long as the decisive event that branches the universe has not yet occurred, these universes remain connected along the timeline.
Of course, they still possess differences. For example, the unique Spider-Totem is a multiversal singularity. Consequently, in these potential futures, it exists in a superposition state of being both present and absent.
This is also one of the peculiarities of the 616 Universe: it possesses the highest number of potential futures. As long as these universes remain potential futures of 616, it is theoretically possible to use a time machine to travel from these worlds back to the 616 Earth.
Take, for example, the task at hand for Kitty Pryde of Earth-811: she needs to return to the past—specifically, to the year 2013, which Earth-811 and Earth-616 currently share.
In the year 2029, superheroes no longer exist, nor do nations or governments. The masters of the world are no longer biological beings, but Sentinels.
To be precise, the world is ruled by a super-Sentinel robot named Nimrod.
Kitty emerged from the ruins of the Baxter Building, carrying a bag of parts that might still be useful. She phased through layer after layer of walls, carefully evading the Sentinel robots that could appear at any moment.
The Nimrod Sentinel—the ultimate form of the Sentinel—was capable of self-repair and self-replication. It possessed the terrifying ability to instantly replicate all X-Gene powers.
Even more horrifying was the fact that, if they so desired, their numbers were infinite.
Kitty came to a halt.
Other survivors had appeared in the distance. They seemed to be ordinary humans, currently fleeing an attack by Nimrod.
[Greetings, Citizen. Please halt immediately for inspection.]
Compared to the earlier iron husks, the Nimrod stood only a little over two meters tall. It descended beside the survivors, scanned them, and then raised its hand. "Your genetic sequence does not contain the X-Gene. However, your DNA possesses a 0.00127% probability of undergoing mutation today to become a neo-mutant. This data has exceeded the threshold."
Kitty held her breath, hiding herself inside the concrete. It was a small trick that allowed Nimrod to overlook her. However, she couldn't stay like that for long; after all, she still needed to breathe.
After a long silence, Kitty descended into the sewers of New York. This place contained various facilities left behind by survivors and the resistance. The sewers, layered over four hundred years from the New Amsterdam era to the present, had perhaps made the New York underground the safest place in the city.
Or perhaps, that was merely a self-deceiving excuse.
"Illyana, I'm back!"
Seeing her companion, who had risked staying here, safe and sound, Kitty was overjoyed. However, the commotion above told them that something was wrong. Illyana immediately pulled Kitty to her side and raised the Soulsword in her hand.
In an instant, a portal enveloped the two of them. By the time the Nimrod Sentinel dug into the sewer, it scanned only the dissipating heat.
Kitty and Illyana returned to the resistance—or rather, the survivors' stronghold. Located in Siberia, it was a former secret Hydra base. They had been here for half a month; so far, it was their safest base.
Returning "home," Kitty breathed a sigh of relief. Seeing her lover coming to check on the noise, she was overcome with joy and threw herself into his arms. "Peter!"
"I'm fine, Kitty. Did you bring back the items?"
"I got them."
As Kitty spoke, she set down her backpack and pulled out a battered robot. It was HERBIE, the Fantastic Four's robotic assistant.
Kitty didn't know why Peter needed it, but Peter had made it very clear—it was for hope.
"I've made contact with some other survivors. Don't look at me like that, Illyana. I know it's dangerous, but compared to what we're about to do, any risk is worth it."
"If you're talking about that stupid idea of traveling back in time to reverse the future, I suggest you forget it."
Illyana sighed. "Remember? Cyclops and his old son who traveled back from 2059... my brother and the others planned to return to 2013, and in the end, they all died. I didn't even have time to pull them away."
"Theoretically, Bishop succeeded. He made it back to the past."
"Then why are we still in this hellhole?"
Illyana's question left Peter speechless. Finally, he let out a helpless sigh. "Then we have to try anyway. We speculated before that physical time travel requires too much energy. We need to change our approach."
As Peter spoke, he began to dismantle HERBIE. He felt a pang of nostalgia for his days interning at the Baxter Building—sometimes adventuring with the Fantastic Four, sometimes fighting crime as Spider-Man.
Now, all of that was gone. Even the people he once wanted to protect and love had vanished.
Now, only the three of them remained of their squad.
His Spider-Sense had long since lost its traditional utility. It wasn't that it stopped buzzing; it was that as soon as they left the unpopulated zones, the Spider-Sense would blare from almost every direction, making it impossible to determine where the danger was coming from.
Conversely, in deep forests like this, the Spider-Sense became a very useful alarm system.
"There's movement outside."
Peter's Spider-Sense buzzed right on cue. He shook his head helplessly and looked at Illyana. Illyana shook her head with some frustration; they had only lived in this spot for half a month.
"Where are we going?"
"To regroup first."
Kitty looked at Peter in confusion and asked, "Doesn't that make us a bigger target? Won't we be easier to expose?"
"But we need to talk face-to-face. Or rather, we need to actually organize a meeting. Time is running out. Illyana, now!"
A red beam of light descended from the sky, blanketed the entire secret outpost, and vaporized a crater over ten meters deep. Nothing was left inside.
Meanwhile, in the heart of the American mainland, within the Nevada desert, three figures phased into a U.S. military bunker. Seeing who had arrived, the survivor waiting there flashed a satisfied smile.
"Look who's here. The Spider-boy with a girl on each arm. I hope you've brought some good news."
Logan spoke with a smirk. Peter simply asked Logan: "Is he here? I need his help."
"I have always been here, child."
An old man walked over, leaning on mechanical prosthetic limbs. His bald head shone brightly, and he looked toward Peter with a gaze that still held onto hope.
"Mr. Charles Xavier, if given a suitable medium, would you be able to project a person's consciousness back into the past?"