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

The GOG.com version includes both the original base game and the expansion: DOOM 3 (v1.3.1) [GOG]

: You eventually learn that Dr. Betruger has defected to the side of Hell, orchestrating the invasion in exchange for power. : The Marine must travel into the heart