: After battling through 25 levels of UAC bases and Hell-warped landscapes, the Marine faces the Mother Demon in her lair and destroys her.

Years after his choice, the Marine is "yeeted" out of Hell by the (the Mother Demon's sister) in an attempt to stop his non-stop carnage. Infuriated by the interruption, he fights through a techbase and back into Hell to eliminate the sister and reclaim his place as the eternal jailer of the damned.

A lone satellite orbiting the planetoid (beyond Neptune) detected the surge in demonic activity. As the only experienced survivor of the original invasions, the Marine is re-commissioned and sent in alone for one last extermination mission. Key Story Beats

: The Marine quickly realizes this isn't just a random outbreak; the demons have intentionally lured him back to finish him once and for all.