Death is visited by Jedah Dohma, who proposes an alliance to achieve equilibrium between life and death on both their worlds. Needing the six Infinity Stones to do so, Death deceives Thanos and Ultron into aiding her, granting Thanos the Space Stone and sending Ultron to retrieve the Reality Stone from
Abel City. Sigma intercepts Ultron, and the two forge their own alliance. They betray the others and use the Space and Reality Stones to merge the two dimensions and fuse themselves into a single being named "Ultron Sigma". To wipe out biological life, they begin unleashing an evolved form of the Sigma Virus that turns organic creatures into synthetic beings under their control. An alliance of heroes from both worlds is then formed. They manage to keep Ultron Sigma at a stalemate until they rescue Thanos from Ultron Sigma's prison and secure him in a containment field at
Avengers Tower. To gain their trust, Thanos reveals the locations of the remaining four Infinity Stones, and teams of heroes are dispatched to find them. Ryu, Chun-Li, Captain America, and Hulk travel to
Valkanda to obtain the Time Stone. Despite Captain America's warnings, Black Panther, the ruler of Valkanda, refuses to surrender it. Ultron Sigma's drones arrive and spread the virus, infecting a Dah'ren Mohran. After Ryu and Hulk defeat the creature, Black Panther agrees to give them the Stone. Next, Dante, Morrigan, Ghost Rider, Arthur, and Doctor Strange travel to the
Dark Kingdom, where they encounter Jedah, who is using the Soul Stone to feed souls to a
Symbiote creature, hoping to use it against Ultron Sigma. While the heroes battle Dormammu and Firebrand, Jedah escapes with the Stone. Meanwhile, Iron Man sends Spider-Man to assist Chris Redfield in infiltrating an
A.I.M.brella facility. There, they find Frank West and Mike Haggar, and discover
MODOK turning people into bio-organic weapons, infused with Symbiotes at Jedah's demand. The heroes defeat MODOK's enforcer, Nemesis, and retrieve the Mind Stone. However, they are soon attacked by Jedah and his giant Symbiote. On
Knowmoon, Captain Marvel, Rocket Raccoon, Gamora, Nova, Strider Hiryu, and X defeat Ultron Sigma's ally,
Grandmaster Meio, and rescue Zero from his control. Upon taking the Power Stone, the station ejects its core, which falls towards
New Metro City carrying a massive Sigma Virus payload. While
Doctor Light, Iron Man, Nathan Spencer, and Hawkeye build a weapon to harness the Infinity Stones, Ultron Sigma attacks
Avengers Tower. In the chaos, Thanos is released and attacks Ultron Sigma, cracking the Reality Stone and forcing them to retreat. The heroes use their Stones to destroy the Symbiote and the falling core, but are infected in the process. The infected heroes then head for
Xgard to infiltrate Sigma's laboratory to finish their weapon, the Infinity Buster. When Thanos learns of Death and Jedah's partnership, he becomes enraged and betrays the heroes, creating a mechanized gauntlet that absorbs Ryu's Satsui no Hadō before departing for revenge. After reclaiming the Soul Stone from Jedah, Dante arrives in Xgard and pretends to surrender the Stone. Since they have no souls, Ultron Sigma is overwhelmed by the Stone and transforms into Ultron Omega. The Infinity Buster is installed into X, who uses it to destroy Ultron Omega. In the aftermath, the virus is neutralized, but since the Reality Stone was cracked, the universes cannot be separated again. The heroes agree to protect the new world and split the Infinity Stones between them to keep them safe. In a
post-credits scene, Jedah tells Death that he has another plan, but Thanos arrives seeking vengeance against them. Believing the Satsui no Hadō is capable of killing immortals like Death and Jedah, he prepares to attack them with a Go
hadouken. ==Development==