Review: MARVEL Cosmic Invasion: The Siege of Castle Doom

MARVEL Cosmic Invasion: The Siege of Castle Doom Review

Developed by Tribute Games and published by Dotemu and Gamirror Games, The Siege of Castle Doom is a brand-new DLC for MARVEL Cosmic Invasion. Released in 2025, MARVEL Cosmic Invasion brought together heroes from the Marvel and X-Men universes to take down Annihilus. Since its release, the developers have introduced two additional DLC characters, but The Siege of Castle Doom is the game’s first major expansion. It not only introduces new playable characters but also adds an entirely new game mode that offers a different way to experience the game. This is our review of MARVEL Cosmic Invasion: The Siege of Castle Doom on PC via Steam, where we try to take down Doctor Doom and explore a castle full of doors.

The Siege of Castle Doom introduces two brand-new playable characters: Doctor Doom himself and Susan Storm, better known as the Invisible Woman from the Fantastic Four. Both characters are available in the new Castle Doom mode as well as the existing Campaign and Arcade modes.

It does feel a little funny playing as Doctor Doom alongside the Avengers and X-Men, considering his position as one of Marvel’s most iconic supervillains. He feels much more at home in Castle Doom, where he serves as the primary antagonist.

There is no officially confirmed timeline for this DLC, but based on its events, it appears to take place before the main campaign. We have already defeated Annihilus by the end of the original game, while Doctor Doom is still working on his own device to defeat him in Castle Doom. This suggests that the events of the expansion take place before the main game’s conclusion.

The biggest change in The Siege of Castle Doom is its approach to gameplay. MARVEL Cosmic Invasion is primarily a traditional 2D beat ’em up with a campaign-focused structure, featuring set levels, enemy encounters, and boss fights that progress in a linear sequence. Castle Doom completely changes this formula by introducing a roguelike, run-based game mode.

Here, you must select your team of heroes and enter Castle Doom to stop Doctor Doom from completing his Cosmic Inductor, a device that he plans to use to destroy Earth while attempting to defeat Annihilus on his own.

The new mode introduces a different progression system built around two meters: your heroes’ Stabilizer and Doctor Doom’s Siege Gauge. Every enemy you defeat drops batteries that your heroes collect to charge their Stabilizers. The more enemies you eliminate, the faster your Stabilizer charges, giving you a way to progress through the castle while keeping the pressure on its defenses.

Doctor Doom has his own Siege Gauge, displayed on the right side of the screen. This meter gradually fills over time and also increases whenever your heroes take damage. If you take too much damage, your characters can fall before the meter is filled, resulting in a failed run. However, taking too long to clear the castle also allows Doom’s gauge to fill naturally. If it reaches its maximum, you will face a fully powered Doctor Doom during the final encounter, making an already challenging fight even more difficult.

This creates an interesting balancing act. You must eliminate enemies quickly, avoid unnecessary damage, and keep progressing through the castle before Doctor Doom becomes too powerful.

To give yourself an advantage, you can visit Reed Richards’ Lab, where you can spend collected resources to purchase upgrades across three different categories: Equipment, Events, and Modifiers.

Each time you begin a new run, you select one option from each category, allowing you to customize the experience and prepare for the challenges ahead.

The Equipment category provides useful combat tools and additional abilities. These include options such as the Helix of Randac, which deals five damage to enemies when they collide with your character for 10 seconds, and the Shield Turret, which allows you to summon a S.H.I.E.L.D. Helicarrier turret for seven seconds.

Events introduce additional challenges that change how you approach individual encounters. Options include Cosmic Storm, which forces you to face enemies without the assistance of Cosmic Swap, and Minefield Menace, which introduces space mines onto the battlefield.

Finally, Modifiers change the overall rules of a run. Perkless, for example, removes the availability of perks but allows Stabilizer construction to restore your hero’s health. Supreme Doom takes things in the opposite direction by forcing you to fight a fully charged Doctor Doom, regardless of whether the Siege Gauge has reached its maximum before the final encounter.

These options add considerable variety to individual runs and give players different ways to approach the challenges inside Castle Doom.

Apart from the selections available at the beginning of each run, you can also discover additional usable items inside different rooms. These provide active bonuses and can turn the tide of a battle in your favor when used at the right time. Some items have multiple uses, but you can only equip one at a time. Once you exhaust its available uses, the equipment slot becomes empty again.

Room progression is another interesting aspect of the new mode. Each door is marked with a specific symbol indicating what awaits you on the other side. Blue symbols represent progression rooms, while purple symbols indicate rooms containing equipment. Red symbols lead to special rooms where you can find infinite ammunition or energy.

There are several other room types as well, and your progression through the castle depends on which doors you choose. This adds another layer of decision-making to each run, as you must balance the need for upgrades and resources against the time and damage involved in exploring additional rooms.

Healing is also considerably more restrictive in Castle Doom. You cannot simply restore your heroes’ health through traditional means. Instead, you must purchase specific upgrades from Reed Richards’ Lab or find special rooms that offer health restoration. Even then, only one hero can recover their health, which makes the decision particularly difficult in co-op sessions when multiple players are struggling to survive.

Staying true to the roguelike formula, if all players in a co-op session lose their heroes, the entire run ends, and you must start again from the beginning. This makes every decision important, particularly during longer periods where losing your progress can be frustrating.

One area where Castle Doom feels a little underwhelming is its environmental variety. The original campaign offers an excellent selection of different locations, but this DLC takes place almost entirely inside Castle Doomstadt. As a result, you spend most of your time fighting through similar-looking corridors and rooms.

There are a few environmental variations along the way, including elevators and dungeons, which provide some visual changes. However, most of the castle retains the same general appearance throughout the experience.

Fortunately, this does not become a major distraction during gameplay. Castle Doom is challenging enough that you rarely have the luxury of stopping to admire your surroundings. Most of your attention is focused on surviving enemy encounters, collecting batteries, and making sure Doctor Doom’s Siege Gauge does not reach its maximum too quickly.

For my review playthrough, I managed to complete a full run after spending nearly six hours learning the mode and working through its challenges. A successful run takes approximately an hour and a half, although the actual duration can vary depending on your experience with the genre and how efficiently you progress through the castle.

If you want to unlock everything available in the new mode, you can expect to invest around 20–25 hours, particularly if you are a slower player. The initial runs can be quite punishing as you learn the different mechanics and encounter increasingly difficult enemies. As Doctor Doom’s Siege Gauge fills, enemies become faster and tougher, while the limited opportunities to restore health make survival even more challenging.

The difficulty is definitely noticeable during the early hours. However, things gradually become more manageable as you invest resources in Reed Richards’ Lab and unlock additional equipment, events, and modifiers. Even after making considerable progress, Castle Doom remains a challenging experience aimed at players who enjoy testing their skills rather than simply breezing through encounters.

The lack of difficulty options is worth mentioning here. Players looking for a more relaxed experience might find the initial learning curve frustrating, especially if they are accustomed to the more straightforward progression of the original campaign.

Coming to the technical side, The Siege of Castle Doom is integrated directly into the main MARVEL Cosmic Invasion client. You can access it through the Castle Doom tab on the main menu, located below Arcade, which opens a separate menu for the new mode.

Since the DLC uses the existing game client, its overall presentation remains consistent with the original release. The visuals and sound design are largely unchanged, with the primary difference being the new Castle Doom location and its associated environments. The new setting is designed well, even if its visual variety could have been better.

During my entire review playthrough, I did not encounter any noticeable glitches or bugs that affected progression or interrupted the gameplay experience. The DLC runs smoothly, and I did not experience any technical issues that would negatively affect my time with it.

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Final Verdict:

The Siege of Castle Doom adds plenty of replayability to MARVEL Cosmic Invasion with its challenging roguelike mode, offering a refreshing change from the original campaign. The new equipment, events, and modifiers keep each run interesting, while Doctor Doom and Invisible Woman are welcome additions. Although repetitive environments, limited healing, and the lack of difficulty options may put off casual players, there is plenty of content here for $7.99. If you enjoy challenging roguelikes and want more out of MARVEL Cosmic Invasion, this DLC is well worth checking out.

Final Score: 8.5/10

Disclaimer: A PC Steam code for MARVEL Cosmic Invasion: The Siege of Castle Doom was provided by Tinsley PR on behalf of Dotemu for this review. For a detailed breakdown of our scoring and review process, please refer to our Review Policy.