Doom 3 (v1.3.1) [gog] -

: The Marine must travel into the heart of Hell, defeat the Cyberdemon guarding the primary "Hell Hole," and use the Soul Cube to close the gateway. Version 1.3.1 [GOG] Specifics

: Unlike the "run-and-gun" style of other entries, the DOOM 3 story emphasizes isolation and darkness. DOOM 3 (v1.3.1) [GOG]

The GOG.com version includes both the original base game and the expansion: : The Marine must travel into the heart

: Set two years later, a new protagonist (another Marine) is sent back to the abandoned Mars base to investigate a mysterious beacon, leading to a second confrontation with Dr. Betruger (now a demonic entity) and the recovery of the "Artifact." -60% DOOM 3 on GOG.com Betruger (now a demonic entity) and the recovery

: You eventually learn that Dr. Betruger has defected to the side of Hell, orchestrating the invasion in exchange for power.

: As you fight through the facility, you discover ruins of an ancient Martian civilization that once fought the same demonic forces. They created a weapon called the Soul Cube , which you must recover from Hell to seal the portal.