This is the first four levels of twelve from upcoming little add-on for Doom II. 

After Doomguy alone managed to get rid of the demons on one of Jupiter's and Martian's moons and Earth, UAC breathed a sigh of relief. Invasion was over.

However, the teleportation experiments didn't stop, nor did the demons' attempts to enter our world.

Fifty years later, after the events that took place in Doom II: Hell On Earth, scientists have achieved impressive teleportation experiments - no more cases where a human could be teleported to Venus instead of a nearby laboratory. 

Meanwhile, the new management of UAC decided to resume teleportation experiments on Fobos, despite the protests of scientists.

UAC management believes that it's been a very long time, and there can be no re-invasion of the demons....

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