- Araña / Anya Banner Corazon
- Invisible Woman / Susan Storm
- Human Torch / Johnny Storm
- Demolition Fist / Flint Marko (first appearance) (flashback and main story)
- Penny Marko (first appearance) (flashback and main story)
- Janice Marko (first appearance) (flashback and main story)
- Hercules (first appearance) (flashback and main story)
- The Leader / Samuel Sterns (first appearance)
- Athena Industries
- Athena Gonzales (first appearance)
- Techpire / Ariel Haven (first appearance)
- Draco (first appearance)
- Medusa the Gorgon (first appearance)
- Cerberus (first appearance)
- Minos (first appearance)
- Wrecking Crew
- Bulldozer (first appearance)
- Piledriver (first appearance)
- Thunderball (first appearance)
- Wrecker (first appearance)
- Kree Empire
- Ronan the Accuser (mentioned only)
- Unnamed soldiers (flashback only)
- Athena of Olympus (first appearance)
- Emma Baker (single appearance; flashback only; deceased)
Bruce Banner / Hulk is having a peaceful lunch in a restaurant with his children Skaar and Anya Banner Corazon / Araña until they get into a fight against the Wrecking Crew Bulldozer, Piledriver, Thunderball, and their leader Wrecker) when they arrive to demolish a nearby university center. Joining them is Thor and his and Hulk's old rival Hercules, and they defeat the crew. Just as all seems well, one of the university's students Janice Marko just advises Hercules that he should not have come "because he is putting himself in danger right now". Hercules takes her words as a threat, but soon prove to be a warning when her father Flint the Demolition Fist storms in and, displeased to see Hercules again, proceeds to attack him.
The two have a terrible fight until Hulk and Thor call them off before the Avengers arrive. As the Wrecking Crew are taken to prison by S.H.I.E.L.D., Hercules takes his leave to avoid more trouble with "ungrateful mortals" while Flint has a moment with his daughter. Hulk explains the team that Flint has become resentful of Hercules because he blames the Olympian for his wife Emma's death; one month before the Oscorp riot, Hercules fought against a squadron of Kree soldiers sent by Ronan to collect Hulk's Sakaarian gladiator armor set (which was buried in the demolition site Flint and Emma were working on), on which Hercules attempted to contain a Kree grenade which exploded, killing Emma and fusing Flint with the armor set in the progress. Noticing that Hercules will get more people in danger in his reckless battles, the Avengers set out to keep Hercules in check while Kate Bishop / Redhawk stays with Flint to comfort him. During which, Iron Man and Captain America overhear news about Athena Gonzales, the CEO of Athena Industries, having ordered the studies of the Eye of Medusa, a dark magic relic which grants the wielder with its namesake's powers. The Avengers are greatly concerned of this because Gonzales (who suffers from a mental illness which causes her to believe she is the dark incarnation of the Greek goddess she is named after) will cause more harm than the heroes believe as long as she has the Eye with her. Hulk and Thor check on Hercules after he defeats Samuel Sterns / the Leader in his mech suit, but noticing the Leader smiling diabolically while taken to prison, Hulk grows suspicious of how Hercules' victory is appearing to have been too easy.
Meanwhile, Kate continues spending time with Flint and his daughters, and shares sympathy with him over his loss of his wife, as Kate still mourns her parents' deaths at the Oscorp facility of years ago, and the two bond and begin going for heroics together as a means of mutual condolence. During which, they battle alongside Susan Storm / Invisible Woman and Johnny Storm / Human Torch against a pack of Olympian monster-based robots (Draco, Medusa the Gorgon, Cerberus and Minos) which were sent by their master to destroy a Pym Industries facility. They defeat the monsters, destroying Medusa although Draco, Cerberus and Minos retreat. Inspecting Medusa's remains, Redhawk and Demolition Fist find out the robots are made of Athena Industries technology. And through the files on one of the devices which controls Medusa for Gonzales, they discover that she plans to use the Eye of Medusa and spoil its powers to subdue "unworthy, pitiful mortals". Meanwhile, Gonzales and her most trusted scientist Ariel Haven (also known as the super-criminal Techpire) continue experimenting on the Eye of Medusa, and using a deeply confident Leader as their test subject. The Avengers and Hercules confront Gonzales and Haven, who refuse to stop their experiment and give away the Eye of Medusa, issuing in a fight when Gonzales summons her robots and also engages Black Widow and Captain Marvel in a fight wielding her technologic spear and shield. Taking advantage of Hercules ignoring Hulk's advice to keep the Leader away from the Eye of Medusa, the Leader soon breaks free and obtains the Eye, becoming more powerful than he is and taking control of Athena Industries' technology.
Gonzales and Techpire attempt to neutralize Leader, but he turns them both into stone and begins wreaking havoc in the facility with the robots. Hercules attempts to once again subdue the Leader, but the villain incapacitates him while taunting that he allowed himself to be defeated by Hercules earlier so that Gonzales would take him to the Eye of Medusa. Just then, Redhawk, Maverick, Invisible Woman, Human Torch and Demolition Fist arrive to reinforce the Avengers. Hulk and Demolition Fist destroy the robots as Maverick (immune to the effects of the Eye of Medusa's powers) strips the Leader of the Eye of Medusa, allowing Redhawk to blow it up with one of her arrows. The Leader attempts to flee, but is caught by Demolition Fist and beaten up. As Gonzales and Haven are taken to be examined and cured from their conditions and Leader is taken in to the Vault, Hercules apologizes for his arrogance and recklessness before returning to Olympus to make amends as the Avengers are visited by the actual goddess of wisdom Athena, who congratulates the heroes for saving the mortals' lives by destroying the Eye of Medusa, while also assuring that Hercules will have proved to have learned his lesson as long as he fully atones for his mistakes. Hulk assumes that Hercules is on his "New 12 Labors", which Athena responds with a chuckle and nod of agreement.
- George Newbern as Hulk / Bruce Banner
- Ali Hillis as Redhawk / Kate Bishop
- Travis Willingham as Thor, Demolition Fist / Flint Marko
- Mick Wingert as Iron Man / Tony Stark
- Roger Craig Smith as Captain America / Steve Rogers
- Kate Higgins as Rescue / Pepper Potts
- Jennifer Hale as Captain Marvel / Carol Danvers
- James C. Mathis III as Black Panther / T'Challa
- Laura Bailey as Black Widow / Natasha Romanoff
- Eric Bauza as Phantom Tiger / Aamir
- Kari Wahlgren as Crystal, Araña / Anya Banner Corazon
- Josh Keaton as Ant-Man / Scott Lang
- Colleen Villard as Wasp / Hope Van Dyne, Penny Marko
- Catherine Taber as Invisible Woman / Susan Storm, Janice Marko, Athena of Olympus
- Max Mittelman as Human Torch / Johnny Storm, Skaar
- Patrick Warburton as Hercules
- Lex Lang as the Leader / Samuel Sterns, Piledriver / Brian Philip Calusky
- Nika Futterman as Athena Gonzales
- Rachael MacFarlane as Techpire / Ariel Haven
- Kevin Michael Richardson as Thunderball / Eliot Franklin, Bulldozer / Henry Camp
- John DiMaggio as Wrecker / Dirk Garthwaite
- Similar to Batman: The Animated Series episode "Fire From Olympus" (on which Maxie Zeus referred to Batman as Hades), each of the Avengers (minus Thor) is believed by Athena Gonzales to be a notable Olympian figure:
- Captain America is viewed as Perseus, the demigod son of Zeus who decapitated Medusa with his shield.
- Captain Marvel is viewed as Eos, goddess of the dawn.
- Iron Man is viewed as Hephaestus, the Smith God.