At some point the wide-eyed Doom Marine, found himself again newly transferred to Mars, the soldier got more than he asked for when Dr. Betruger betrayed the UAC.[3]
During his battles to protect Earth, he found himself trapped in hell fighting an eternal battle with the demons. He would travel across time and worlds to save the multiverse. Sometimes finding himself pulled to battle other Champions from other worlds and alternate earths in the Arena Eternal (in this earlier period, he received new armor, that fit like a glove).[4]. He continued to be a great champion defending many worlds from the demons and killing them in Hell.
The Slayer's Testaments described him as an ancient and mystical time-traveling warrior called the "Doom Slayer" or "Hell Walker" who was either banished to Hell or chose to stay there (possibly a reference to Doom 64's ending). The Doom Marine proceeded to rampage his way across Hell for "eons" as an unstoppable force of death and destruction, becoming an icon of fear to all demons.
His one-man war was only ended after
he was lured into a trap, allowing the forces of Hell to collapse one of their temples on top of him. Entombed inside a stone sarcophagus, he was sealed away in the Kadingir Sanctum, hopefully forever. Unfortunately for the demons, the Doom Marine's sarcophagus was eventually retrieved by the UAC (on one of the alternate earths) and brought back to Mars. Sure enough, after Hell commences its invasion of Mars, the Doom Marine awakens as bloody-minded as ever. He then arms himself with a pistol, reclaims his Praetor Suit and begins to fight the hordes of hell once more. After he saves Earth, he is captured by Hayden and put into stasis again, while the scientist prepared his next plans.