This challenge is related to that Cult of Bones thread that came up earlier, but with a much better twist.
Phase 1Your dwarfs must build a sky fortress stemming from a single support and up stair. The support must be accessible by dwarfs. You may dig out underground, but no buildings may be constructed there - tough luck if you breach a cavern full of cave swallow men! The exception is for constructions (like pump stacks) that will eventually end up aboveground. Then, preparations should be made for Stage 2.
Prep for Phase 2- Pump stacks are allowed, but all other constructions from the surface must be in separate buildings connected by bridge so that they do not provide support for the main sky fortress. The bridges will open towards the sky fortress so as to seal it off in case of emergency.
- The pump stack will be needed for well water and farming, since it'll all be on constructed floors.
- Outbuildings like the pump stack can be protected by wall at the base but MUST only be big enough to do their job - no dwarfs will be allowed to loiter!
Phase 2Once you hit 80 dwarfs or 100,000☼ of wealth, everyone files one by one into the sky complex. The hapless migrants left behind must deconstruct the up stair and leave the sky fortress to its luxury-filled life in the clouds. A system must be set up for the left-behinds to fire useful goods and artifacts into the sky fortress, or possibly a minecart rail (see above for rules on this). The no-underground-constructions law is repealed, but only for the bottom-dwellers.
The sky fortress is on its own for population. If every dwarf succumbs to a particularly nasty flying beast attack that shoots syphilis-causing dust out of its eyeballs, then it must remain alone forever. On the flip side, it's getting valuable goods constantly so it shouldn't be doing too badly.
ProductionEveryone in the sky fortress is one of the lucky early adopters. It should be a sustainable building without the flow of goods from below, so that means indoor mud flats to grow trees on and farm plots. You will also farm herds of top-quality livestock in expansive underground pastures, but they will have to be kept under control so you don't have fifty thousand cows stinking up the place. However, leave professions for growth - if you have an indoor tower-cap farm then there's no reason not to have some decent carpenters on hand. They will also live in the lap of luxury. This means at least 3x3 bedrooms for everyone, and they will live like nobles. Give them a bed, a chest, a cabinet, an armor stand, a weapon rack, and hell, throw in a nice metal or stone statue imported from below. They also get the nice foods, so grow sun berries and wild strawberries instead of plump helmets and sweet pods. Good industries to be placed upstairs are the meat, clothing and leather industries - rock and metal isn't sustainable (easily).
The ones who have been left behind can start their own fortress, but all they can eat is plump helmets and dwarven wine (the sky-dwellers want their slaves to be somewhat efficient, so no cruel alcohol deprivation). Prepared meals are to be loaded onto the Rich and Famous Express. When the nobles begin to arrive, they can all live underground in the same conditions as the unwashed masses. They are also the only ones allowed to trade.
Moving ThingsPreferably, the minecart(s) doing the moving are made out of solid gold. Everything goes on it - artifacts, masterpieces, prepared food, rocks that your favored citizens prefer (omg microcline dis is de hapiest day of mai lief!!!!!), metal crafts, cloth, extracts... the list goes on and on.
As for waste dumping, you live in a sky fortress for a reason! Don't settle for dwarven atomsmashers when you can settle for taking potshots at the unfortunates scurrying below. Keep track of who's been maimed or killed by falling xcave spider silk socksx or worse! A peasant is two points, a baby or child is one, a miner's five, a noble is twenty, and everyone else is three.
ArchitectureHonestly, this is up to you. But lots of glass windows are recommended - who doesn't like being able to see the giant cave bats trying to menace your fortress bang into a ☼crystal glass window☼ until they spiral to the ground of concussions? Bonus points for having bedrooms with glass ceilings - prevents cave adaptation AND provides a scenic view of the white storks your military has shot down! Think the castle from Howl's Moving Castle, you want lots of little decks and windows looking out on the world. Expand organically as you grow.
DefenseOh. Right. The single support. That needs defending, doesn't it? Yes it does! The only rule is that it
must be accessible from all four directions and
nothing can be built within two squares (measured in a 5x5 square, not some sissy elven circle) of it. From that point on, the sky's the limit, really (HAW). Restrict trap use for a superdorfbonus. Have it defended by ballistae manned by the mushroom-sucking bottom-feeders. Include a defense system to pump magma from the great magma sea, then route it through your fortress and pour it on enemies! This is why I mentioned pump stacks - it's always good to have a steady supply of magma. Drop socks on goblins! Mass-pit ornery cats on them! If fall damage is too lethal, take advantage of it!
This should be a fun challenge, because it's a weird mish-mash of aboveground challenges, split-fort challenges and equality/inequality challenges, plus the added Fun of a doomsday support that will crash your entire fort to the ground.
Watered-Down VersionThe constant threat of having 80+ dwarves get blown across the continent in a gigantic cloud of billowing dust getting to you? Just build an actual wall (preferably out of soap or gold or something) and continue as normal. It's not as dwarfy but you still get to experience the power of being in a sky fortress.
Additional NotesGhostDwemer knows that this is impossible because pump stacks are teh cheatinge and I only typed it to waste his time. THE ILLUMATI STRIKE AGAIN!