Marvel's Secret Invasion was one of the most complex and wide ranging stories of the last few decades. It was a narrative that redefined the structure of the Marvel Universe for quite some time and actually built genuine tension thanks to the identity aspect brought in by the Skrull's shapeshifting.
While a Secret Invasion has been confirmed for the MCU, it hasn't yet materialized. However, the actual comic book storyline was so long ago that many fans actually forgot some of the core and shocking elements of the story. Ahead of future MCU developments, it's important to revisit why the Skrulls are so dangerous.
10 Difficult Detection
One of the most vital aspects of this storyline was the fact that the Skrulls were completely undetectable. In the past, there were ways to tell if someone was a Skrull shapeshifter, but the species had actually evolved.
Using sleeper agents, there was no way to truly tell who was a Skrull. No sorcery, spider-sense, or intuition could predict who could turn next. Eventually Reed Richards would invent a device that allowed for the detection of these monsters.
9 It Started In Japan
The whole story actually started in Japan, before the Secret Invasion really kicked off. After a fight between the Avengers and Elektra, Echo stabbed her through the stomach, killing her. The dying assassin turned into a Skrull.
This sparked a huge controversy and brought all versions of the Avengers into the fold, despite the various allegiances following the Civil War. It was unclear whether this was an isolated incident in Japan or something far bigger.
8 Spider-Woman's Manipulation
Spider-Woman was one of the few Skrulls who seemed to know her role. As the Queen she adapted to each situation quickly. The character became very manipulative early on and there's signs that this wasn't really Jessica Drew throughout the Avengers run.
In particular, the character started to spread blame as to who else was a Skrull. She even manipulated events to move the body exactly where she wanted it, allowing her plan to come into full effect.
7 The Illuminati Cover Up
The Illuminati were eventually given Elektra's body, but the group had already been covering up the potential invasion. They had knowledge of it and were trying to bypass the event in order to protect the Marvel Universe.
But they were attacked by one of their own, when it was revealed that Blackbolt was actually one of the sleepers for a long time. This caused a lot of dissention amongst the Illuminati, which is why the Skrulls managed to get one step ahead.
6 Tony's Mental Breakdown
Tony Stark is actually suffering from a mental breakdown throughout the Secret Invasion. In fact, he has a complete crisis, thanks in larger part to the manipulation of Spider-Woman. He is unaware if his actions are his own.
She tries to convince him that he is really a Skrull and that's why he acted as he did during the Civil War. His real identity is confirmed by the end of the story and it has catastrophic consequences as to how Stark truly sees himself.
5 Savage Land Activation
The Secret Invasion officially began in the Savage Land when all of the sleeper agents were actually activated. This came after an Avengers team and a set of fake Avengers arrived in the Savage Land, following the crashing of a Skrull ship.
Luke Cage accidentally set off the beacon and the attack began across the globe. The Savage Land was the site of much of the major conflict for the Secret Invasion, with the rural location at least protecting Earth's citizens.
4 Major Coordinated Attacks
The Skrulls had orchestrated a much larger plan, where their invasion managed to target a number of different areas. They therefore took out a number of key threats, which they felt would stop their progress.
The Baxter Building was sent into the Negative Zone for instance. Jarvis was replaced by a Skrull and started to hack into Avengers security systems. Even the S.W.O.R.D. base was blown up thanks to Dum Dum Dugan.
3 Beta Ray Bill's Escape
Beta Ray Bill was another character that the Skrulls deemed to be a threat. He was therefore one of the few that was actually kidnapped and trapped on one of their stations. He eventually made his escape.
Returning to Asgard, he was met with the mischievous Loki who tried to drum up suspicion that Beta Ray Bill was actually a Skrull himself. Thor came to his aid though and he was proven innocent with Mjolnir.
2 Abigail Brand's Secret Ability
Abigail Brand is a very useful member of S.W.O.R.D. who sought revenge after her base had been destroyed. She's picked up a number of tricks over the years, but one skill managed to save hers and Reed Richards' lives.
She had learnt how to speak Skrull and therefore made her way round the ships pretending she too was a Skrull in disguise. The plan worked and it was once again a signal that she is one of Earth's finest protectors.
1 The Shot Heard Round The World
The shot heard round the world seems like an over the top title, but it really was the gunshot that changed the history of the Marvel Universe. Norman Osborn was the man to pull the trigger on the Queen Skrull.
As a result, he was given a lot of new responsibilities and became head of S.H.I.E.L.D. It was this decision that eventually lead to the Dark Reign; without that single shot there wouldn't have even been the Siege of Asgard.