Doctor Doom took over the world of Marvel Comics last year, and he's not stopping there in 2026. Robert Downey Jr.'s Doctor Doom will debut in December's Avengers: Doomsday, and just this month Doom has led a team of fighters in Marvel Tokon: Fighting Souls. In between those appearances, Doctor Doom will have another starring role. Doom-centric DLC is coming to Marvel Cosmic Invasion this fall.

On Monday, developer Tribute Games and publisher Dotemu announced The Siege of Castle Doom for its retro beat-'em-up. The paid DLC "will find the infamous Doctor Doom central to an all-new game mode arriving alongside two new playable characters," according to a news release. Tribute Games and Dotemu are currently holding their cards close to their vest as they did not specify who those new characters will be or if Doom himself will be playable.

The Siege of Castle Doom will be Marvel Cosmic Invasion's second DLC after a character pack brought Cyclops and The Thing into the side-scrolling action earlier this summer. They joined a roster that included Marvel staples like Spider-Man and Wolverine, but one that also included somewhat obscure characters like Phyla-Vell and Beta Ray Bill.

The brawler was received well and currently holds an 84% Critics Recommend score on OpenCritic. "Like its arcade ancestors, [Marvel Cosmic Invasion] is a simple, easy-to-pick-up, enjoyable-to-replay action game — ideally played cooperatively," Polygon's Michael McWhertor wrote in his review.

Marvel Cosmic Invasion: The Siege of Castle Doom will be released in fall 2026 for Nintendo Switch, Switch 2, PlayStation 5, Windows PC, and Xbox Series X. A specific date and the DLC's price were not shared at this time.