# MARVEL Cosmic Invasion DLC adds Siege of Castle Doom mode for Linux and Steam Deck

> **Key takeaway:** The Siege of Castle Doom DLC for MARVEL Cosmic Invasion launches November 10th on Steam with day-one Linux and Steam Deck support, adding a timed roguelike mode with branching paths, 12 perks, and two new playable characters.

**Published:** 2026-11-07T15:27:27+00:00 
**Source:** Linux Game Consortium 
**Category:** open-gaming 
**Canonical URL:** https://fosswire.org/news/marvel-cosmic-invasion-dlc-adds-siege-of-castle-doom-mode-fo.html 

## Summary
Tribute Games Inc. has unveiled gameplay for The Siege of Castle Doom, a downloadable content expansion for the cooperative brawler MARVEL Cosmic Invasion. The DLC introduces a new timed mode where players must reach Doctor Doom before a Siege Gauge fills, with enemy difficulty escalating as time passes. The mode features branching routes, 12 unlockable perks powered by Battery Cells, and persistent progression through Reed's Lab that carries across runs. Two new fighters join the roster: the Invisible Woman and Doctor Doom himself, the latter available as a playable character in the mission to stop his own plan.

The base game, which has attracted over two million players, was developed by Tribute Games using their FNA engine and published by Dotemu. The Siege of Castle Doom DLC releases on November 10th across Steam for Linux, Steam Deck, and Windows. Linux gamers should note that this represents continued commercial support for the platform from a studio with established open-source engine credentials through FNA.

## Gameplay systems and Linux platform support
- **Timed roguelike structure:** The Siege Gauge creates escalating difficulty during each run, with enemy ferocity increasing as the gauge fills, forcing route optimization under time pressure.
- **Branching path design:** Castle Doom splits into multiple routes that change between runs, creating variable encounter sequences rather than fixed level layouts.
- **Perk and progression economy:** Battery Cells earned during runs unlock 12 distinct perks spanning defensive, offensive, and utility categories, while Reed's Lab provides cross-run unlocks for gear, events, and custom rule modifiers.
- **FNA engine foundation:** Tribute Games builds on their established FNA-based toolchain, which has historically provided native Linux support without Proton translation in their previous titles.
- **Day-one platform parity:** The DLC launches simultaneously for Linux, Steam Deck, and Windows, with the base game already verified for Steam Deck play.

## Why it matters
Native Linux releases from established studios like Tribute Games reinforce the commercial viability of the platform for independent developers, particularly those using open-source-adjacent engines like FNA. For Steam Deck users, day-one verified support for DLC content ensures the handheld remains a consistent target for cooperative multiplayer titles without compatibility uncertainty.