Final Doom

Final Doom is a first-person shooter video game that uses the game engine, items and characters from Doom II. It consists of two 32-level megawads (level files), The Plutonia Experiment by the Casali brothers, and TNT: Evilution by TeamTNT.

TNT: Evilution
In TNT: Evilution the UAC once again are intent on developing and experimenting with dimensional gateway technology. They set up a base on Io, one of the moons of Jupiter, with a solid detachment of space marines for protection. The marines do their job well: when the first experimental gateway is opened they annihilate the forces of Hell. Research continues with more confidence and all security measures turned at the gateway.

A few months later, the yearly supply ship comes ahead of schedule, and looks strange and unusually big on the radar. The lax radar operators decide that there is nothing to worry about... The personnel of the base go out to behold the terrible truth: it is a spaceship from Hell, built of steel, stone, flesh, bone and corruption. The ship's enormous gates open to unleash a rain of demons on the base. Quickly, the whole facility is overrun, and everyone is slain or zombified.

The main character, the nameless space marine (who was revealed to be the marine commander on the moon) has been away on a walk at that time and thus escapes death or zombification. After being attacked by an imp, he rushes back to the base where he sees the demonic spaceship still hovering above it and realizes what has happened. Then he swears that he would avenge his slain troops and sets out to kill as many demons as possible.

In the end, the marine defeated the "demon spitter" and the game describes "something rumbles in the distance. A blue light glows within the ruined skull of the demon-spitter.

Plutionia Experiment
After Hell's catastrophic invasion of Earth, the global governments decide to take measures against any possible future invasion, knowing that the powers of Hell still remained strong. The UAC is refounded under completely new management (the old trustees and stockholders were all dead anyway) and aims at developing tools that would prevent demonic invasions.

The scientists start working on a device known as the Quantum Accelerator that is intended to close invasion Gates and stop possible invasions. The experiments are carried out in a secret research complex, with a stationed detachment of marines. The work seems to be going well but the creatures from Outside have their attention drawn towards the new research. A Gate opens in the heart of the complex and unnatural horrors pour out. The Quantum Accelerator performs superbly: the Gate is quickly closed and the invasion is stopped. Research continues more boldly.

On the next day, a ring of 7 Gates opens and an even greater invasion begins. For 1 hour the Quantum Accelerators manage to close 6 of the Gates... but the Hellish army has become too numerous and too strong. The complex is overrun. Everyone is slain, or zombified. The last Gate of Hell remains open, manned and guarded by a Gatekeeper - a powerful, enormous and ancient demon that has the power to open Dimensional Gates and control or protect them.

The government, frantic that the Quantum Accelerator will be destroyed or used against humanity, orders all marines to the site at once. The player, the nameless space marine, was on leave at the beach. He was also closest to the site and gets there first. There he discovers that there is much demonic activity (howling, chanting, machine sounds) within the complex - the Gatekeeper is obviously working on something, and his work would soon reach some awful climax. He also realizes that when the marines arrive, they would not be able to penetrate the heavily infested complex, despite the firepower and support they will have. The marine decides to enter the complex and stop the Gatekeeper alone.