John Grimm

He's like the Mad Max of Doom!

History
Literally, five seconds after the events of Doom (2005), which had happened in 2046 AD, the portal that had been blown up somehow reactivated and sucked in both Grimm and his sister. He was startled awake only for a few moments after the teleportation, where he saw Foxy taking his sister away to be his "Arr, pirate queen and shit, aw man!" and then he fell back into unconsciousness.

Sooner or later, he retrieved his sister from Foxy, only for her to get kidnapped by Daniel. Somehow, we have a quote of him going "Aw shit, here we go again." Naturally, he saved her once again. Anyway, he found himself in Hell on account that he got 2 free passes to the Hells-Coaster Ride. Of course, it took him a few months to get there because people kept kidnapping his sister for some reason. At one point, he joined the Hell Troopers due to their insurance policy and tendency to not have family members kidnapped every day.

After riding the Hells-Coaster, the siblings both got an honorary pass to stay in the city of Gula for a few weeks. However, while Samantha Grimm (his sister) was able to stay there, John's time as a Hell Trooper finally started. His first few years began with touring the prison cities of Hell, along with a year station at Limbum, The Walled city.

then the Abyss happened. Sometimes news is really slow and the news of The Abyss invading Hell wasn't just really slow, just didn't happen? Seriously, where was that courier, the news boy? Oh right, Hell doesn't have that, they operate off of Crimson King internet. I guess Archdemon Satan must have disguised himself as the "Crimson King" and told the internet not to let any news come reach the rest of Hell so he could lead a big surprise attack.

200 years later, Limbum was still under attack by the Abyss, when Archdemon Lucifer destroyed the city. Grimm was pretty much the only survivor, but he himself was made unconscious for about 25 years. (Man, Hell is weird!) Once he woke up, he made his way to Gula, which had fallen by then. Hoping to see his sister, he did... unfortunately, she was not alive. This threw Grimm into a rage which carried him into the heavy flow of the Abyss. After many years, he found himself in the Abyss, finally level headed. Seeing that the portal to Hell was still open, he figured that closing it on the side of the abyss would likely save Hell. Of course, he didn't really have a reason to, but due to not having anythng else to do and a Hell Troop oath to live for, he closed the portal anyway. And now he is lost to us, bit of a downer ending, don't you think?

Trivia

 * If you have his initials JJG, and subtract the first J by 8 and the second J by 4, you get BFG. Pretty cool huh?
 * Not sure if he landed on Deimos during the Heaven Invasion or a completely different time. Either way, he was definitely in Hell during the Heaven Invasion.
 * He doesn't really seem to age, and is still looks to be in his prime. This is likely due to the C24 serum which was injected into him during the events of Doom (2005).
 * Due to surviving through the entirety of the Heaven Invasion, we can correctly assume he's effectively immortal. I mean he could still probably died, but he hasn't yet I guess so he's being called immortal.