In an article I put out about a week ago, I accidentally dove into a tangent regarding the possibility of Dark Reign showing up due to a Civil War theory I crafted. This also fits into the second half of my first theory which can be found here.
[Potential Spoilers for Captain America: Civil War, Captain America: Winter Soldier, several comic arcs (listed later), and Phase 4 of the MCU.]
So, as a quick reminder, or if you're just not gonna open the other link, the theory was simple: Bucky is the new version of Ragnarok and he is thus at the focal point of Civil War. Unlike the Civil War comics, vilifying Iron Man is not the primary purpose of the new Ragnarok, so instead he's just the connection to a greater evil or something to that effect.
Now that we've got that out of the way, let's consider the concept of the Dark Avengers themselves. Well, the long and short of it is that this is the culmination of several stories that actually began with Civil War and ended with Siege. The full list of stories this encompasses are as follows: Civil War, Secret Invasion, Dark Reign, and Siege in that order. I understand that not everyone is aware of these stories, and a year ago, I admittedly was not aware of them myself. However, I would like to take the time to give a proper explanation for those seeking more information (if not, just scroll down to the next header):
A Brief History of Marvel from 2006-2010
Let's start with 2006-2007 with Civil War or more importantly, the creation of Ragnarok. The character on the right (with the yellow/red lightning) is Ragnarok. To tell the difference, his costume is that of the original Thor whereas the real Thor's costume changed following his death during the Norse Ragnarok (basically the end of the world) shortly before the events of Civil War.
Ragnarok is a robotic clone of Thor. He was created by Tony Stark in collaboration with Hank Pym (Ant-Man) and Reed Richards (Mr. Fantastic) with the sole purpose of giving the Pro-Registration side of the war an advantage in taking down Cap's resistance and arresting heroes. However, the plan blew up in their faces when Ragnarok took justice into his own mechanical hands and killed Goliath, a member of Cap's resistance and close friend of both Hank Pym and Stark. They were obviously more cautious about sending Ragnarok out into the world after that point. This was also the tipping point of Civil War and Stark's point-of-no-return in the sense that he slowly became the villain of the Civil War story.
After this event came the Secret Invasion - a return to the Kree/Skrull War story arc from the 1980s:
In late 2008, the Secret Invasion began. The Skrulls are a race of aliens with the ability to change their form and adapt to the powers of various heroes. Their "super soldier" is known as Super Skrull because he has all the powers of the Fantastic Four.
It turns out, the Skrulls had returned to Earth and begun infiltrating the ranks of our beloved heroes years ago! One of the people kidnapped and replaced was none other than Reed Richards himself. In this capacity, the Skrull were able to manipulate Stark into imprisoning plenty of heroes in the name of the law along with altering the programming of Ragnarok to turn him into a Terminator instead of a Vision.
Ultimately, the Skrull Queen is killed and the entire invasion is ruined before it can come to fruition. However, S.H.I.E.L.D., previously run by Tony Stark thanks to his involvement in Civil War, is in shambles and in need of a new leader. That's where Norman Osborn of all people steps in.
Norman Osborn is given control of S.H.I.E.L.D. because he convinced the government H.A.M.M.E.R. would be a better alternative to S.H.I.E.L.D. given its failure to prevent the Skrull invasion (the acronym for H.A.M.M.E.R. literally has no meaning). With this new form of power, Osborn decides to create a new version of the Avengers known as the Dark Avengers. This leads into the Dark Reign and Siege stories (almost done I promise).
Osborn's team of Dark Avengers is actually comprised of villains posing as members of the Avengers team. Osborn himself dons the Iron Patriot armor, Venom takes the form of Spiderman, and Ragnarok takes the place of Thor just to name a few positions. Dark Reign involves Osborn abusing said power via running H.A.M.M.E.R. and the Dark Avengers.
This doesn't last long and in 2010, the Siege story starts.
The real Avengers don't take too kindly to imposters posing as them. Their plan to infiltrate H.A.M.M.E.R. and end the Dark Reign turns into an all out assault (or siege) on the organization. Obviously, the Dark Avengers are defeated and order is once again restored to the world.
So, that just about sums up Marvel's main story arcs and how they relate to Ragnarok over the course of 4 years. However, this is after all a theory and that's where my plan comes into play:
How This Fits into My Phase 4 Idea
My idea for Phase 4 (which can be found in the second link at the top of the article) was that H.A.M.M.E.R. would come into existence. As noted by the climax of Winter Soldier, S.H.I.E.L.D. technically no longer exists. That opens the door for a new organization to come to fruition, à la H.A.M.M.E.R. Spider-man: Homecoming will most likely see the introduction (or already established) Norman Osborn and, depending on how they spin it, he could very well become an extremely powerful villain, if only for a short period of time.
I can see it starting out subtly at first - a few imposter heroes pop up in solo films. A Spider-man sequel could shine some more light on the darkness surrounding H.A.M.M.E.R., and the epitome of the film, the Avengers film, sees the heroes finally taking a stand against Osborn in the climactic Siege storyline. The Dark Avengers are thus defeated and all is, probably, right in the world. A similar situation to the Thanos reveal could be something along the lines of Osborn meeting with the Skrull Queen claiming he's failed only to have a series of screens light up behind her revealing the identities of heroes that have been replaced by the Skrulls.
Now that obviously leaves some questions open: Why is Osborn working with the Skrulls? Which heroes have been replaced and how will we know? How does any of this connect back to Phase 5?
All of that could be revealed slowly throughout Phase 5 until the big reveal in the Avengers film which could be the start of the Kree/Skrull War. That could leave Phase 6 for retelling the stories of how the heroes coped with the war, the events that led to the war, etc with the war itself being the Avengers 6 (that's a name I find difficult to fathom).
In terms of replaced heroes, I think a healthy mix of new and old heroes is in order. It would be interesting to introduce new heroes that turn out to Skrull with a proper introduction to them later; however, I also feel that popular actors such as Chris Evans and Robert Downey Jr. could step in as their old roles as Skrull as well. It would certainly make for an interesting turn of events when the audience is left to question which characters are Skrull especially with the new arrival of old heroes from before Infinity War.
I haven't fully fleshed this last part out yet. It started with that first theory where I conceptualized a tentative Phase 4-6 plan which I've attempted to expand upon here. However, if you have any suggestions on how this idea could be better executed, let me know! As always, I'm willing to give credit where credit is due.