After a few moments, explosions rock the facility, causing machinery to crash to the floor and sending boxes falling off shelves. Cut to: a red portal, with a number of ghostly skulls flying out of it. They rip through the installation's personnel, changing them into something …not quite human.

Elsewhere in the facility, you duck into a corner when a huge shadow suddenly envelopes the area. The creature attached to it is at least a few feet taller than you, and it's hard not to feel overwhelmed as it slowly lumbers by. You smartly choose not to fire your pistol as the creature passes, oblivious to your presence … for now.

This is DOOM III, and it's going to scare you to hell.

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