Seriously, MASSIVE SPOILERS.
Wardedcanyons was founded in a terrifying biome, deep within goblin territory, to fortify the dwarf border with against forces. The wildlife was a constant challenge, as were the endless sieges and ambushes - for four years not one caravan was unharmed. But the military gradually improved, and the fort thrived.
Until one day, an overeager adamantine miner chipped into a hollow tube which carried the screams of the dammed upward. Fortunately a quick-thinking mason closed off the mine tunnel that led there, providing what turned out to be only the illusion of safety.
Months after, a weaponsmith hard at work at his magma forge noticed a strange sound, just as a hideous slug-like demon erupted from the magma along with half a dozen of his friends. The lower caverns were in chaos until the military arrived, and an epic battle ensued that claimed the lives of two legendary speardwarfs. The openings that fed the forges were closed forever, and the wood burner was put back to work making charcoal.
Over the next couple years, an occasional demon would slip into the fortress by mysterious means. Eventually the mayor got an idea - since the demons' numbers had already been depleted, why not journey even deeper and venture into their domain? Tunnels full of mechanized spears and a trapped bronze colossus were built to lure out any remaining demons, to no result - the demons remained in their pits.
Finally the expedition was mounted - shafts were sunk through the adamantine into the chambers of hell and stairs built swiftly down to the slade surfaces. Unfortunately the demons' numbers were not so depleted as hoped, and only ferocious combat and the sacrifice of appalling numbers of lives (including that of our brave queen) allowed a foothold to be established:
Years of further preparation (and strict instructions that no pigtail socks of demon victims were to be collected) were necessary for the expansion of the foothold into a useful space. After many more sacrifices, a larger space was built and a lovely sculpture garden was built around a masterwork statue of the god of victory:
The first visitor to the Garden of Hell, seen here, was the last survivor of the original seven - a miner horribly crippled in an early battle, come to see the fruits of ten years of labor. The earth was struck - to the gates of hell and beyond!!!
Thoughts on the experience:
I hadn't planned on trying to colonize hell until so many demons had come up that I figured I should try to take advantage. My plan to lure the remaining ones up to their doom was totally unsuccessful - apparently they only do the clown car thing when you first puncture the tube. Penetrating downwards would have been easier except that off-duty dwarfs inexplicably all wanted to go wandering around in hell with no goal. I'm not kidding - dozens of them all went running out the first moment a staircase touched slade. Then, of course, their buddies tried to collect their belongings after they were massacred. The militia had a similar problem of spotting a demon way on the far side and running over to challenge it. I lost all my legendary fighters from them dodging into eerie pits. Sigh. All in all, I think about 150 dwarfs died to make this work. If I do it again, I could make it a little more efficient, but I have no idea how to stop the flood of no-job idiots from killing themselves. I found that the timing was critical - I had to watch the demons closely, and when they were off exploring magma tubes, I would try to build a couple walls. I think the way to make this work best is to plan to catch the original wave of demons, and then immediately get to work. Oh, and how awesome was it that the first tourist in the outpost was the last surviving founder?!?