The Paul Dini Superman cartoon was pretty good. I’ll explain.
Darkseid is a DC comics villain. I’ve only really seen him in the Superman cartoon; I mean, he’s in the DC universe but I’m only so informed. He’s the God-King of Apokalips, the hell-world. He leads armies of flying parademons and hovering dragon tanks. He gives the cartels Apokalipsian technology and they do heists for him, he opens Gates and makes clean getaways. He has a sexy, sexy bass voice. He tries to turn Earth into blasted and buring Apokalips. It’s visually striking.
That’s what The Iron City is like. It’s a fucked up colonial post-industrial amoral society, using teleport gates and spanning worlds. There are haves and have-nots, and the haves are 10 challenge ratings higher than the have nots, and get their rocks off rubbing that in. They have steel, and magic, and curses, and germ warfare, and techno music, and a utilitarian philosophy and the full resources of a constellation of worlds.
They grant their servants guns. Their gunpowder is powered by the dead; it’s made of people. It doesn’t work in direct sunlight, so they blacken the skies in front of their armies first; oil fires, storm summoning, whatever.
They grant their servants other spirit-powered tricks, too; a form of cheaply forged black spirit-mithral that’s hard as nails but, wouldn’t you know it, thirsty for blood sacrifice to keep it running. They have imps in bottles, and possessed jewelry, and drugs and poisons.
Actually, they’re a lot like D&D classic drow!
Their armies are three, at least: whatever local militia is available, the actual literal devils in the MM, and then the dead and damned of a dozen worlds; zombies, ghouls, wights. The graves open up and vomit forth. Then they get issued rifles.
They want souls for all of their technology — really, all of their everything. Their walls are made of the dead; their swords and armor, their carriages, their meals. It’s all fresh and tortured, not because the dead deserve it, but because the Iron City demands it.
They conquer. They pick a world, they establish a beachhead, they harvest the world. This can go fast if the resources are easy to extract, or agonizingly slowly, if the resources are renewable.
People are a renewable resource.
They don’t really want you to sign over your soul; they want to make the world worse, they want to fill it with greedy shortsighted people, and most of all they want to conquer Heaven, because their goals are directly opposed.
They’re based out of the titular Iron City, a planar metropolis called Dis whose wards cover multiple worlds via large, stable gates. With checkpoints. It turns out that Cathule isn’t actually in conjunction with Dis — rather, the Black Roads cut from Cathule to a hellscape called Gehenna, which conects to Dis.
Gehenna: the sky is writhing worms. The earth is poison and serpent trees. The undereorld is an infinite labyrinth. It is permanently locked in conjunction with Dis, Celestia, and Cathule, and absolutely brimming with Abyssals. That last is the fault of the Celestials or of the Iron City; each blames the oher, but the act which converged Cathule and Gehenna was a mighty working that the Celestials disrupted, opening the rift, and so now it is a multisided war through which unfortunate mortal souls often wander.
So: let’s say you’re a pretty normal guy. You die near a church. The priest says the words. Likely you don’t even go to Gehenna, but go straight to one of the Heavens, because there’s a nice celestial waiting who can guide a Black Road therr. Or maybe you do wind up in Gehenna, but you’re on a list, there’s an honor guard looking for you already, and they’ll get you out of there.
Maybe all this is true, but in life, you weren’t so nice. You’re basically not going to fit in in paradise. Now, maybe that’s not a problem: paradise can absorb a certain amount of not-a-team player. But maybe they’re full up, or maybe you really put the crimp on an angelic project, or maybe you were just in the wrong place, wrong time.
A lot of spirits shelter in Gehenna until the winds of that place unmake them. Another larva grows. Others take shelter in the labyrinths. Others are eaten by the hungry dead, the abyssals, or (and here wd get to the point) seized by the slavers of the Iron City.
These bands of Iron City slavers need supplies; raw materials, warm bodies, warm food. Nothing useful grows in Gehenna, and the supply chain from Dis is too long. Now we understand the colonies in places like Cathule: they service the reaping bands, which harvest what dead they can from those same worlds and their neighbors.
Hell isn’t just one place, but it sure is badly managed. The Celestials are right when they say a paradise awaits the faithful, but getting there can be real expensive.