Secret Invasion: 10 Things You Need To Know About The MCU's Next Big Event
9. It All Started With Elektra
While the Avengers battled ninja clan the Hand, Echo stabbed their leader Elektra in the heart, killing her. As Elektra dropped to the ground, Earth's Mightiest Heroes were shocked to witness her corpse revert to that of a Skrull.
Even though this wasn't the first time a Skrull impersonated a superhuman, this revelation shocked the Avengers to their core. Elektra is a masterclass ninja and assassin, and yet the Skrulls managed to defeat and replace her without anyone noticing. Even though the Hand is one of the world's most secretive and paranoid groups, they never suspected their mentor was a fraud. Wolverine, who can normally detect anyone based on their scent, also failed to notice the person he was facing wasn't the real Elektra.
Because the Avengers stumbled upon this alien by chance, it meant that it was very likely there were more Skrulls in their midst that they were unaware of. Although the Skrulls hadn't intended to begin their takeover of Earth at this point, exposing this Elektra as a decoy put a spanner in the works. Left with no choice, the Skrull Empire pre-emptively initiated a full-scale invasion.