Ever since Marvel relaunched their line of comics under the Marvel Now banner, a majority of the company's biggest titles have been focused on time travel.
It all began with All-New X-Men, by Brian Michael Bendis and Stuart Immonen.
In the first issue, a distraught Beast brings the original X-Men – including the teenage version of himself – to the present in order to rattle his former teammate Cyclops, who recently killed their mentor Charles Xavier while possessed by the Phoenix.
But in the current Battle of the Atom crossover, the young X-Men have been demanded to return to their era.
And the X-Men of the future have come back in time to make sure this happens.
At the end of the Age of Ultron mini-series, also by Bendis, the space-time continuum is revealed to be broken due to years of time travel shenanigans in the Marvel Universe.
Over in Guardians of the Galaxy, also by Bendis, a cabal of intergalactic leaders are concerned about earth's heroes constantly meddling with the space/time continuum without regard for how that impacts the rest of the universe.
In an interview with Comic Book Resources last year, Bendis hinted at a crossover between All-New X-Men and Guardians of the Galaxy that would deal with the ramifications of the X-Men's time travel through the universe.
The obstacles and adversaries the cast of "All-New X-Men" will confront come from around the globe and the farthest reaches of space. "The original X-Men coming to the present day will have consequences, and this goes back to something I mentioned in our 'Guardians of the Galaxy' interview. It's my feeling that every one of these space-time continuum abuse acts has a butterfly effect. Sometimes it happens directly to the abusers, and sometimes that effect happen across the galaxy. I may not feel like there's some immediate fallout right here on Earth, but somewhere, something is happening. You know how 'the butterfly flaps its wings and there's a hurricane in Africa?' The Marvel version of that is the original X-Men travel time and have an adventure. Then, across the galaxy, something happens. We're going to discover what that is in both 'All-New X-Men' and 'Guardians of the Galaxy.'"
The aftermath of Age of Ultron is picked up over in Indestructible Hulk by Mark Waid, in which the time-traveling villain Zarrko claims that history can now be transformed at a whim.
Zarrko – who is something of an unreliable narrator, maybe – taunts Bruce Banner by suggesting that the Hulk's erratic personality is the result of others manipulating the timeline.
This is not a new idea in comics. DC has rebooted its continuity three times over using similar tricks to make sense of conflicting stories over the years, or recreate characters from scratch.
There's plenty of other rampant abuses of the space/time continuum going on throughout the Marvel Universe.
Over in Uncanny Avengers by Rick Remender, the time traveling Kang the Conquerer is in the midst of an elaborate era-spanning plot to rid the world of mutants by manipulating the heirs of Apocalypse.
This plot goes all the way back in time to Ancient Egypt, where Kang first met Apocalypse as the Pharaoh Rama-Tut...
...and in the present, where an older future version of Kang called Immortus warns Captain America about his younger self's scheme.
The Spider-Man of 2099 has come back to the present day over in The Superior Spider-Man by Dan Slott.
The Thor of the present teamed up with the Thor of the past and the future over in Thor: God of Thunder by Jason Aaron.
Wolverine's half-brother Dog Logan is a time traveler over in Wolverine and the X-Men, also by Aaron.
Eva Bell, a new mutant who has joined the cast of Bendis' Uncanny X-Men, has the power to manipulate time.
Magik, another character in the Uncanny X-Men cast, has the power to teleport through both time and space.
The cast of Jonathan Hickman's New Avengers re-assembled the villain Thano's all-powerful Infinity Guantlet...
...but when they used it, all of the infinity gems were destroyed except for the time gem, which disappeared.
Notably, the covers of the Infinity miniseries, in which Thanos is the main villain, correspond to the colors of the infinity gems...
...except for the final issue, which is white rather than orange, like the missing time gem.
This is notable because in an early chapter of the story, Thanos learns of this, and begins his quest to find the time gem.
All of this strongly suggests that Marvel's top creators are building towards a major story that will connect all of these threads, and radically change the continuity of the Marvel Universe.
Another major storyline in Hickman's New Avengers, Avengers, and Infinity has to do with the gradual destruction of thousands of alternate earths, and the imminent doom of Marvel's primary earth, which is known to fans as Earth-616.
This is very, very similar to the premise of DC Comics' classic 1986 miniseries Crisis on Infinite Earths, which consolidated all of DC's timelines and alternate realities into one rebooted universe.
But will Marvel actually reboot entirely, like DC recently did with The New 52?
Or will all of this simply result in a slightly modified version of Marvel's history, as hinted by Zarrko's dialogue from that issue of Indestructible Hulk?
