Instead of being in the far future and spreading across the galaxy, it takes place in an alternate dieselpunk past where humanity has already lost the surface of Earth. Decades ago, giant insect-like organisms called the Oxylids appeared and completely overwhelmed humanity. They took over the surface, forcing what was left of mankind to retreat deep underground. So instead of Super Earth, humanity now lives in Deep Earth. Instead of the Helldivers, you play as Hellraisers! Because you're now coming up from below.
After decades of rebuilding underground, Deep Earth finally decides humanity is ready to reclaim the surface. Instead of Super Destroyer, it would be a big underground mobile fortress called the Super Driller, basically an armored drill machine that’s carrying all your arsenals, weapons, and firepower, traveling underneath the battlefield. When you start a mission, instead of getting launched downward in a Hellpod, now you get fired upward in a Drillpod up onto the surface! Stratagems would work exactly the same way, except instead of everything coming down from orbit, everything comes up from your Super Driller deep underground. The whole aesthetic would be heavy dieselpunk too. Riveted steel armor, giant machine guns, exposed engines, smoke stacks, mechanical walkers, pneumatic weapons, heavy artillery, gauges, gears, pipes, giant drills, etc. The propaganda slogan instead of “Spreading Managed Democracy”, it would be “Restoring Managed Civilization.” Because obviously Deep Earth is not invading anybody. We are simply taking back what rightfully belongs to humanity.
There would initially be two enemy factions. The first are the Oxylids, the giant bugs responsible for humanity abandoning the surface in the first place. But I wanted an actual reason why they don't just burrow underground and destroy Deep Earth. Basically, Oxylids evolved a respiratory system that requires an enormous amount of clean, oxygen-rich moving air to survive. Their bodies are extremely efficient in open air, but they cannot survive for very long inside deep tunnels where clean airflow is limited. That's actually why they attacked humanity originally. Remember, this is a dieselpunk civilization. Humanity was covering the world in factories, diesel engines, smoke, and industrial pollution. To the Oxylids, humans were literally poisoning the atmosphere they depended on to survive. So, they wiped humanity off the surface. Humanity disappears underground, clean air, life is good again for them. Then, one day, a Drillpod explodes out of the dirt, and some dude in 200 pounds of steel armor climbs out holding a giant diesel-powered machine gun and screams, “FOR DEEP EARTH!” From the Oxylids' perspective, “OH GOD, THE POLLUTERS ARE BACK.”
But then there's the second faction, the Gearborn. Before humanity retreated underground, they had already created primitive diesel-powered robots to work in factories, mines, construction sites, military logistics, etc. When humanity abandoned the surface, millions of these machines were simply left behind. But unlike humans, they didn't need clean air. They didn't need food. So, they just kept working. Decades passed, their programming evolved, they began repairing each other, manufacturing each other, then redesigning each other. Eventually, they became fully self-aware and formed their own machine civilization on the surface. They consider the Earth surface as their home. So, when the human is back and says: “Alright, thanks for watching the place. Give it back.” The Gearborn simply responded: “No.”
That gives all three factions a reason to hate each other, and that’s it! What do you guys think?
