Tribute Games and Dotemu have finally explained what The Siege of Castle Doom actually is. The second paid add-on for MARVEL Cosmic Invasion, due November 10, adds the Invisible Woman and Doctor Doom as playable characters, and its new mode turns out to be a run-based assault on Doom's home in Latveria, with branching doors, a perk tree and a tug-of-war between two gauges that decides whether Doom gets his way. Until today the studio had only said the mode would centre on Doom. A developer post on the PlayStation Blog now lays out how it works.
What Doom was doing during the Annihilation Wave
The base game throws Marvel's heroes at Annihilus and his insect armies. The DLC's premise asks where Victor Von Doom was while all of that was happening. The answer: building the Cosmic Inductor, a powerful and unstable device he thinks will let him beat Annihilus on his own and make him Earth's champion. Naturally that also makes him a threat to everyone else, so the heroes have to storm Castle Doomstadt to stop the device from charging.
The two new heroes fit that story. Doom fights in his own tech armour and leans on occult magic and raw intellect, and the store page hints that you may end up recruiting him against Annihilus rather than only fighting him. Susan Storm brings the Fantastic Four's light-bending and force-field powers, which the studio describes as abilities the game has not had before. Reed Richards is not playable, but he guides the run through voice-over while Doom taunts the invaders from the other side.
Two gauges, one castle
The heart of the mode is a pair of meters working against each other. Each time the heroes are beaten inside the castle, a Siege Gauge rises and Doom's Cosmic Inductor gains power. Each win, on the other hand, drops Battery Cells that fill a Stabilizer, Reed's own invention for keeping Doom's machine in check. Fill it enough and you earn Stabilizers to spend on upgrades. Let the Siege Gauge run away from you and the final confrontation gets much harder.
The studio says it wanted a mode with far more replay value than the campaign's stage-by-stage structure, and the numbers back that up: The Siege of Castle Doom has more than five times as many encounters as the main game, and that is before you count its new events, traps and hazards. Routes run through the Halls of Doom, lined with medieval torture equipment, along battlements caught in blizzards, and up the Tower of Solitude, where Doom's experiments sit beside moving elevator platforms.
Choosing a door
You do not move through the castle in a fixed order. At the end of a room you pick one of several themed doors, and each one promises something different:
- Equipment gives a special power, such as a force field or an energy blast.
- Events send the team into an arena where the rules change for a while, with a bonus or a penalty depending on how it goes.
- Heal restores health.
- Infinite grants a stretch of unlimited ammo or unlimited focus.
- Progression pays out a random number of batteries towards Reed's Stabilizer.
That makes route choice the main decision of each run: take the safe heal, or gamble on an event to build the Stabilizer faster.
Perks, Reed's Lab and unlocks
Stabilizers feed a perk system with three branches, Offense, Defense and Tactical, and twelve perks in total that can boost defence, throw damage, ammunition or healing. Perks are applied per hero, so a co-op team can split the roles between them. In multiplayer, an MVP screen at the end of a run highlights whoever contributed most.
Between runs you can visit Reed Richards' lab to spend Stabilizers on permanent unlocks: new equipment, new events and modifiers that change how later runs play out. Finishing a run also unlocks a new colour palette for the hero you used, and the pack adds fresh palettes for the whole roster plus new music from Tee Lopes, who scored the base game.
Release date and platforms
The Siege of Castle Doom launches on November 10, 2026, and needs the base game. MARVEL Cosmic Invasion is available on PC, PS5, PS4, Xbox Series X|S, Switch and Switch 2, and the DLC's Steam page is already live for wishlisting. A price has not been announced yet. For reference, the first add-on, Cyclops and The Thing, sold for $3.99 when it launched in May.
Unlike that first pack, which only added two characters to the existing campaign, this one is pitched as a whole new way to play, so it is the bigger of the two drops by some distance.
