A developer has successfully embedded Doom within the interactive terminals of Ultrakill, allowing players to toggle between the 1993 FPS and the diegetic shop interface. The integration leverages existing Unity-based Doom ports—namely managed-doom and DoomInUnityInspector—to render the game in real-time without disrupting Ultrakill’s core mechanics.

Ultrakill’s terminal system, reminiscent of Prey or Deus Ex, enables seamless UI interaction without pausing gameplay. This mod extends that functionality, letting players invoke Doom via a smiley-face icon on the terminal screen. Controls revert to classic WASD/arrow movement and Ctrl for firing, while mouse input remains tied to Ultrakill’s first-person perspective.

Ultrakill Now Runs Doom Inside Its Terminals—Here’s How to Deploy It

Deployment Requirements

  • Ultrakill installation: Purchase and install the game from Steam.
  • BepInEx: Download the latest win_64 release for Windows 11 (adjust for other OS versions) and place it in the Ultrakill directory (C:\Program Files(x86)\Steam\steamapps\common\Ultrakill). Run Ultrakill once to finalize setup.
  • Doom assets: Provide a DOOM.wad file from a retail copy (e.g., Nightdive’s re-release) or the shareware version. Note: Custom WADs like MyHouse are unsupported.
  • Mod files: Extract ultradoom.dll and ultradoom.wad from the GitHub repository into the BepInEx/plugins folder. Create a doom subfolder in the same directory and place both WAD files there.

No additional configuration is required—simply interact with the terminal’s smiley-face icon to launch Doom. The mod preserves Ultrakill’s mouse controls, allowing players to glance away from the terminal without losing progress.

Technical Underpinnings

The project builds on two prior Unity-based Doom ports: managed-doom, a C# rewrite of the engine, and DoomInUnityInspector, which adapted it for the Unity . Squaresweets’ work bridges these tools to run Doom in a live game environment, demonstrating Unity’s flexibility for embedded game systems.

Ultrakill’s development continues, with the next major update slated for mid-2026. Meanwhile, this mod underscores the enduring adaptability of Doom’s engine—now running inside another FPS, complete with diegetic immersion.