Impossible City

The Impossible City was originally created as the sentient headquarters for a group of unknown heroes, who defeated and imprisoned the Ashen Combine within the City itself. Once those heroes disappeared under unknown circumstances, the Ashen Combine escaped their captivity. The Citysmith and Meridian Diadem altered the city to serve their needs, the former infecting it with an invasive superstructure while the latter erased its memories and made it unable to act against their will. The Impossible City's prior name was erased by Meridian Diadem as part of the purge of its memories. Out of a twisted sense of amusement, they left the Impossible City's conscience intact so that it could suffer as it watched them destroy worlds. For an unspecified amount of time, the Ashen Combine traveled the multiverse using the City as their headquarters, ravaging cities and killing the heroes that protected them. This continued until the Ashen Combine arrived on Earth-616, where they battled that reality's Avengers. While most of the team battled the Ashen Combine across Earth, Captain America and Black Panther were sent to destroy the villains' headquarters, unaware that it was sentient. Black Panther planted explosive devices all over the City's exterior, only for the City to speak to the two Avengers for the first time. Certain that the Avengers could not defeat the Ashen Combine, and hoping to prevent any further destruction, the City planned to destroy itself, only to be faced with opposition from Black Panther and Captain America, who refused to let the City give up its life. Once the Ashen Combine were defeated, Black Panther triggered the explosives he'd placed across the City, targeting the Citysmith's invasive superstructure. Once the explosives went off, the superstructure was destroyed, freeing the Impossible City from the Ashen Combine's control. With the villains trapped inside it once again, the Avengers' heroism inspired the Impossible City to ask if it could join them, which they accepted.