Superhero teams are one of the cornerstones of the comic book industry, and the Avengers are a big part of that. Stan Lee and Jack Kirby created the group in 1963 as a response to the Justice League superhero team created by Marvel Comics’ archrival, DC Comics, three years prior. The founding members of the Avengers were Ant-Man, Iron Man, Thor, Hulk, and the Wasp, but their numbers have since grown exponentially.

Joss Whedon brought the team to life on the big screen with The Avengers in 2012. His film brought together the dysfunctional heroes of the Marvel Cinematic Universe and turned them into a force to be reckoned with — both in-universe and in real life. Of course, what audiences saw in the movie is only an inkling of the team’s potential, and a mere snapshot of their comic book roster. Many heroes have fought alongside the Avengers over the years, some of which people didn’t even know were ever part of the team.

Just like every other superhero squad in comic books, Earth’s Mightiest Heroes have branched off into different subgroups over the years, such as the New Avengers, Secret Avengers, and Mighty Avengers. These spinoff teams only add to the 15 Heroes You Didn’t Know Were Avengers.

15. Mantis

0.mantis 15 Heroes You Didnt Know Were Avengers

Pom Klementieff made her debut as Mantis in James Gunn’s Guardians of the Galaxy Vol. 2 earlier this summer, and she will be reprising her role in Anthony and Joe Russo’s Avengers: Infinity War next year. Which is only fitting, considering that Mantis was once of the most prominent members of the original Avengers team in the comics, having made her comic book debut in The Avengers #112 in 1973, created by Steve Englehart and Don Heck.

Her history with the superhero team is quite complicated, seeing as she was recruited when the Swordsman attempted to rejoin the team in the ’70s. During her early years, Mantis fought alongside the Avengers against enemies such as the Collector, Dormammu, Loki, and event Doctor Strange (during the Avengers/Defenders War). Having her officially appear in an Avengers film is a big deal for the character. We just hope that the Russo brothers make proper use of her powers.

14. Venom

Flash Thompson as Agent Venom 15 Heroes You Didnt Know Were Avengers

Venom is one of Spider-Man’s perennial enemies, though some of the people who host the symbiote stray on the side of an antihero. One of the latest characters to be bonded with the symbiote is Flash Thompson, who willingly submitted himself to the alien upon the promise that he would be able to walk again, following the loss of his legs during his tour in Iraq. Unlike past hosts, though, Flash only bonds with the symbiote for short periods of time — no more than 48 hours — otherwise the alien would take full control over him.

Flash used the alien symbiote to become Agent Venom. He ended up joining the Secret Avengers team in Secret Avengers Vol. 1 #23 six years ago, before eventually joining Thunderbolt Ross’ superhero team, predictably named the Thunderbolts. After a few years fighting alongside both teams, the Avengers tasked Agent Venom with joining the Guardians of the Galaxy as their official envoy. With Flash Thompson joining the Marvel Cinematic Universe in Spider-Man: Homecoming, could Agent Venom be in the character’s future?