

The Plutonia Experiment is one of the two official 32-level Doom II IWADs that form Final Doom. Developed by brothers Dario and Milo Casali under contract for id Software, it was launched on June 17, 1996, alongside its companion title, TNT: Evilution.
In *The Plutonia Experiment*, following Hell's devastating assault on Earth, world governments take decisive action to prevent any future incursions, aware that Hell's forces remain formidable. The Union Aerospace Corporation is reestablished under entirely new leadership (the previous board and shareholders were all long dead) with the goal of creating technology to thwart demonic invasions. Researchers begin developing a device called the Quantum Accelerator, designed to seal invasion Gates and prevent further breaches. The project is conducted in a covert research facility, guarded by a marine detachment. Initial progress appears promising, but the entities from the Beyond take notice of the new activity. A Gate erupts at the center of the complex, unleashing unspeakable terrors. The Quantum Accelerator proves highly effective, swiftly closing the Gate and halting the invasion. Encouraged, the research team pushes forward with renewed determination. The following day, a ring of seven Gates materializes, marking the start of an even larger invasion. For one hour, the Quantum Accelerators manage to shut six of the Gates, but the demonic horde is now too vast and too powerful. The facility is overwhelmed. All personnel are either killed or turned into undead husks. One final Gate remains open, protected by a Gatekeeper: a massive, ancient demon with the ability to open and control interdimensional portals. Panicked over the potential destruction or misuse of the Quantum Accelerator, the government dispatches all available marines to the site immediately. The player, the unnamed space marine, was on vacation at the beach. He is also the closest to the facility and arrives first. Inside, he detects intense demonic activity—howls, chants, and mechanical noises—the Gatekeeper is clearly working on something, and his efforts are nearing a horrifying conclusion. The marine realizes that when the other marines arrive, they will be unable to breach the heavily corrupted complex, no matter how well-equipped they are. So, he decides to enter alone and stop the Gatekeeper.