Castles in the Sky Part I: History, Mechanics and Trade

Friend of the blog @slyflourish asked me to give “the treatment” to a world of flying castles.  It turns out trying to cover all facets of a world where fantasy, flight, and large cargo movement intersect takes more than a single column so I broke this into two.  For the introduction we will take a look at the economic history, core mechanics and implications of triangle trade of flying castles. Next week, we will look at religion, war and conquest.

Castles in the Sky: History

Once in a while people put aside their unlimited desire for racism and war to give into a baser impulse: trade.

Trade is a simple concept. I have a thing here that took my local resources to produce and is unique to my environment. You have a thing there that took your local resources to produce and is unique to your environment.  I would like your thing. You would like my thing. Let’s exchange and we both have the things and we are both richer for it.  And we will sell what we traded into our local economies at an enormous mark up and make a fat payday.

Overland trade is the simplest method to execute but carries the most risk for the lowest payout.  While anyone can fill a wagon with goods and head to parts unknown, the road hides dangers: weather, disease, hostile governments, the dreaded Head Tax, unforgiving terrain, long trip times, bandits, war, and spoilage.  A dromedary, the best vehicle for crossing desert, tundra, steppe and mountains, transports about 1/2 a ton per animal.  A dromedary train of 50 provides almost 50Klbs of trade goods. The payout is good, but the risk forces people to search for better methods of transport.

The sea is orders of magnitude less risky and more profitable than the road.  A single caravel carries up to 50 tons of trade goods – twice an entire dromedary train for trips half as long.  And the sea removes some risks – bandits, mountains, desert, the Head Tax, random wars – for different risks of equal or higher value – starvation, scurvy, pirates, storms, and getting lost at sea.  Yet, the large cargo space, maneuverability, shortened trip times, and higher profits convinced countries to invest heavily in sea ports and naval technology.

For most of history, with only occasional levitate spell, the sea was the preferred method of trade until land was unavoidable. Cargo rode in ship bellies and took short, overland trips to reach final destinations. Merchant adventurers boarded ships to lands unknown and returned with holds full of spice, rare weapons, textiles, and gems. Ports grew and flourished.

Air travel is vastly preferable to either overland or sea trade. Unhindered by terrain with the shortest possible trips between two points, air travel tantalizingly promises vast riches.  Whoever got themselves up there, traveled from point A to point B, filled a hold with goods, and returned, would win the game of trade.

A merchant wizard named Silenius Vox made his fortune on sea trade. He retired and invested his gains in magical experimentation.  First, he levitated his outbuilding a couple of feet and hovered it overnight.  It crashed and splintered in the morning.  Fresh off his victory, he retooled the spell and levitated the barn.  It crashed.

Silenius Vox, obsessed, worked for years furiously levitating this building and that. He burned all his cash on reagents and apprentices attempting to make the buildings move.  Near to giving up and despairing at a lifetime of failure, Silenius changed a single mystical word and made his breakthrough.  The Vox Mass Levitate spell ripped his manor house from the ground, flew it 3000 feet in the air, and, pushing apprentices into service to maintain the spell, held it there. Victory at last!

Silenius Vox passed away soon after but his apprentices continued the research.  Maturing to Master Wizards, Silenius Vox’s former apprentices perfected the Vox Mass Levitate spell.  They levitated houses for the wealthy and powerful.

Spells of such incredibly utility attract government attention. Before the third set of apprentices matured to Master, the King pressured and bribed wizards to develop a bigger, grander, and more powerful spell.  The true maximal extent of the spell was the castle. Attempts to levitate palaces or walled cities failed when reaching some unknown scalability limit in the spell.  No amount of money, wizards, power or reagents extended above this constraint; a standard sized castle was the best the Vox Mass Levitate could do.  Yet, this was not wasted effort. During the discovery of spell’s limits, the wizards figured out how to move the castle in three dimensions.

This was the key.

Soon, Flying Castles wreaked slow motion havoc upon the flying castle-less neighbors.  A period of open warfare and conquest followed where those without Flying Castles fell to those who did.  It was an age of darkness and death from above.

But, governments could not keep this valuable technology secret.  Thieves and spies made off in the night with the spells.  Assailants kidnapped wizards and tortured them for their knowledge.  Technology spread to the nations until the Flying Castle-less and the Flying Castled were at parity.

Wars never stopped, as they never do, but the Flying Castle technology fell into merchant class hands.  While local wars are great for profits, long distance trade was better.  A Flying Castle carried 1000 tons of cargo space over the caravel’s 50 in a single round trip.  Nothing, not wars, nor pestilence, nor death slows down the urge to trade and make great profits.

The great Port cities turned into the great Flying Castle docking cities.  Warehouse space flourished.  The rich took out massive shares in trade expeditions. Companies formed around Flying Castles.  Soon, majestic Flying Castles dotted foreign skies.

Castles in the Sky: Mechanical Considerations

A flying castle needs two features to operate: a continuous magic spell keeping the castle airborne and a method of locomotion.

Early in Flying Castle Technology when the apprentices and grand-apprentices of Silenius Vox still lived, singular wizards and their apprentices kept the castles aloft.  The Vox Mass Levitate spell requires 24 hour maintenance, refresh and reagents to keep airborn.  Should the spell stop, the castle, an unaerodynamic box made of rock, plunges majestically but quickly to the ground.  In the first Flying Castle years before merchant companies perfected maintenance, sad crashed remains of failed experiments and lax apprentices lay side-up and parapet-down in distant cow pastures.

During the period of war and conquest, teams of military-inclined wizards lived in the castle and worked in six hour shifts.   The spell’s high level strain was incredibly taxing. The mortality rate among apprentices forced to keep a Flying Castle battle-ready was appallingly high.   Keeping a fleet of military-ready Flying Castles looked prohibitive.

Death is the sort of problem ingenious minds solve and solve they did.  By time the Flying Castles fell into the hands of merchants, countries employed three solutions:

  1. Offer wizards and their teams substantial shares of the trade.  More than a few wizards made their fortune on a single round distant trip across the world, exchanging magic items for silks and porcelain, and returning alive and whole.  It’s deadly on the apprentices who carry the burden of maintaining the spell during the flight but financially rewarding for the Master Wizard.  However, this is not particularly financially rewarding for the merchants who put up the stake, finance the expedition, and absorb all the risk.  The merchants would rather not share all their shares of the trip with the wizard. But this works, and many Flying Castle Trade Companies employ this method.

  2. Impress the magical-wielding “dark races” (Dark Elves, Fiends, Demons, Illitids, etc) into service via Murder Hobo-based conquest.  Invade their lands, take their children into Mamluk-like slavery, train them into strict magical arts, and force them to spend their lives flying castles.  In these realms, the King himself owns these slaves. They are property of the state and leased to merchant use for heavy fees and taxation. And, dark races raised as wizards to fly castles often end up as powerful magical castes within their originating and slave-taking societies – carrying its own risks.

  3. Gnomish and other tinkering societies use a magic item/mechanical approach. They build enormous magic engines to automatically feed reagants and spell maintenance into the Vox Mass Levitate spell.  This requires no wizards or slaves, but the merchant must bring on a team of gnomes for engine maintenance, give up cargo space for the engine, and risk suddenly plummeting from the sky should the engine seize up and the spell cease operation. But Gnomes are adventurous sorts. They often join the Merchant Company as members, invest their own money in the expedition, and perform their own engine maintenance. And the engines are mostly reliable. There’s only been a few massive crashes in the last few years…

That leaves the merchants with solving locomotion.  After generations of development, and combined with supplementary magic spells, the box-like and air resistant flying castle has three methods of direct movement:

  1. Enormous magic sails.  Fly high enough in the sky and the powerful trade winds will push a castle along the trade wind route.  This method requires a navigator with strong knowledge of the trade winds, careful map reading, compasses, and recognition of known land masses from the sky.  It also needs a man at arms who runs a tight sail maintenance crew.  This is the safest and most common method of moving flying castles from destination to destination.

  2. Ley Lines.  Smart wizards tap into the ley lines running along the ground and use them as a “super highway” for flying castles between cities.  They can draw the power up into themselves and expend it as propulsion.   This method allows faster travel than sails but requires both the ley lines staying put and flowing where the Flying Castle needs to go – neither always true.  It also requires a wizard on board.

  3. Gnomish technology to rig up combinations of magic engines, windmills, and unspeakable bits of steampunk to gather wind up the front and expend it out the back as propulsion.  This will get the Flying Castle where it wants to go, when it wants to go, in the direction it wants to go, with no limits on travel or movement.  It might also explode.

Ingenious minds work today solving the air resistance problem.

With levitation and movement solved, Flying Castle merchants, captains and engineers must solve a number of other thorny issues:

  1. Landing is not something a Flying Castle can do in a foreign port unequipped and unexpecting an enormous flying fortress full of merchants, boxes and goods. Wizards, should they be available on the flight, provide levitation “elevators” to move cargo to and from the ground – the Vox Mass Levitate spell is good for more than moving houses and castles.  Those Flying Castles staffed with gnomes employ dirigible and hot-air balloon technology to move seamlessly from sky to ground.   These dirigibles carry a ton of cargo, collapse into storable containers and reinflate with heat.  And, like other gnomish technologies, they occasionally explode.

  2. Flying castles can still get lost in a heavy storm, deep fog, or prohibitive cloud cover.  Navigational magics and charting technology advanced rapidly once air travel became possible but the remains of lost castle still lie in forests, various deserts, and crashed into mountain tops.  Blowing out to sea is the biggest risk for Flying Castles. The featureless ocean gives no clues to lost navigators.  Navigators are armed with locational magics to navigate them back toward land in case of storm. Lost at sea means running out of food and starving, or killing the magic team keeping the flying castle aloft and disappearing into the ocean, lost forever.

  3. Food is less an issue on Flying Castles than on long distance sea voyages but still faces similar restrictions.  The food does not rot from exposure to salt water.  Castles have larger cargo warehouse spaces for food than ships.   With green open areas, Flying Castles carries cattle (which has an issue, see #5), growing plots, and fruit trees. But without refrigeration – somewhat solved by magic –  food will spoil. The green areas cannot feed the entire crew and merchant passengers, only supplement to hold off scurvy. Smart navigators plan food refuel stations along their routes to ensure the crew does not starve.

  4. “Dumping” is a real legal issue for Flying Castles.  In the first salient and heady years of flight, captains solved the issue with waste by dumping it over the side on the unsuspecting people below.  Those living on the path of trade winds or ley lines learned the hard way they were under Flying Castles. Before long, dumping became an issue of international concern and a body of legal entanglements.  Today, captains allocate a percentage of valuable castle cargo and living to magical waste containment and management while flying over any known and populated lands or treaty areas.  The gnomes have solutions which a few enterprising captains have installed, but the explosion risk is often too high for captains to contemplate.

Otherwise, living in a Flying Castle is much like living in a cross between a ship on a long distance voyage and a regular castle.  It’s comfortable to passengers and ideal for long distance hauls through the sky.

Castles in the Sky: Trade

Triangle trade is a simple and extremely profitable concept. An example:

  1. High Elves desire silver as they melt the coins down and turn them into jewelry.  In return for chests of silver, they sell their carefully hand-crafted ghostly textiles, super common to them but rare to everyone else.

  2. The Dwarves, who have strained relations to the High Elves but not with the people flying castles, exchange the holds of Elven textiles for Dwarven magical weapons and armor.

  3. The Murder Hobos at home pay premium price (in silver) for Dwarven magical weapons and armor which they use to murder various indigenous demi-humans for more silver.

Around and around the Flying Castle goes, taking a markup at each step, and selling to those who want things and buying oversupply.  This is not limited to Elven textiles and Dwarven magical weapons – Flying Castles trade in rare and precious magic items and spells, spices, other textiles, rare food stuffs, inventions, technology, finished goods, and beings from far away continents.

Nations and merchants cave to the urge to maximize their profits. One castle is great. It brings home 1000 tons in possible profit. Two castles are better.  A treasure fleet of castles is best.  Five castles flying together lowers risk from loss on the voyage, almost guarantees someone returns home, and, at its most optimistic, delivers almost 5000 tons of cargo back to the Mother Nation. Who doesn’t want a treasure fleet?  The might, the majesty, the awe, the sheer projection of wealth and power of five castles hanging with a slight hint of menace over foreign skies and distant ports is worth it.

Although this sort of thing has drawbacks. One country, in the quest to conquer its neighbors, sent out a fleet of its entire nation in castles on a single triangle trade mission and returned with warehouses full of goods for sale. Too bad they ripped up their entire border defense in search of profit. Their neighbors took advantage of a castle-less nation devoid of wizards and invaded on their own recognizance.   By time the trade mission returned, they had no home nation to return to.

This was a lesson in moderation. You can send your castles, but you cannot send all your castles.  (Note, the trade fleet did fine – they just declared a new nationality and sold in foreign currency.  Merchants don’t care about governments. They only care about trade laws.)

Later, wise nations invested in castle building for the express purposes of turning them into flying cargo trade fleets. But the lesson held – and those who learned this lesson developed their fleets for both trade and war.

An interesting facet of the triangle trade available to the Flying Castle and expressly unavailable to ships or overland travel is the ability to finish goods while in transit.  The castle has space for:

  • Warehousing components;
  • Warehousing advanced and finished goods;
  • Feeding and housing artisans who can take components and complete finished goods.

This requires merchants to give up precious cargo space to production space. He could stuff more Elven textiles per square footage in his castle instead of providing airy and sunny work spaces.  The merchant must make this financial call: if the finished good fetches a higher price in the market than the cost of finishing the good on board plus the loss of other possible sales, he will commit to hosting on-board artisans.  Some trade missions do. Some don’t.

Those who choose to produce in-flight expressly target trade ports selling raw materials: cotton for thread, molasses for rum, reagents for complex spells, mithril and adamantine for magic weapons.  Artisans produce small but high performing goods in their on board workshops.  By time the Flying Castle reaches the next port, the merchants can flip what was a buy of raw materials as highly priced finished goods.  Then they can purchase the very best of the best their host nation has to offer – the porcelain bowls, the highest quality coffees and teas – and ship them back home for maximum profit.

And thus, theoretically, everyone makes money.

Problems crop up in the otherwise tame and civilized triangle trade when two nations both want a monopoly in one rare and valuable good. For example, both Flying Castles wish to sell a high performing rare Elven mithril armor crafted only by one tribe of Elves living on a distant and nicely tropical island. Controlling that good – and the island – and monopolizing it allows one nation to reap the profits while the other nation to pay sky high and price-controlled prices.  The potential profits are huge.

It’s in the best interests of Murder Hobos, and the two nations, to try to control that island, its goods, and its inhabitants.  In go the swords and mercenaries.  One might think the Elves on the island making armor would have something to say about all this. But to have a say, they need to get a Flying Castle. Right now what they have are coconuts and really nice hammocks.  The Elves are out of luck.

Here the nations do what nations do.  They do enter into far off hostilities.  They ship fireball-throwing cannons instead of cotton thread.  And they get into a hot shooting war over islands and Elves.

And now we know how they work and why they go places, Flying Castles fight!  Next week, we sail religions around the world, launch ground invasions, drop bombs, dog fight and go to war over trade goods and land!

Image Credit: Art by Jaydot Sloane of Vanity Games –


  1. Brandon Van Every says:

    This of course is a technology of movement that modern humans have not even come close to achieving. We *do* have naval craft now that are as large as “castles”. I’d point out that any spell that can work in the air, would probably work better in the water, as water gives lift to the vessel. Also if the vessel drops, at least it doesn’t have to fall very far, i.e. hovercraft.
    The form of actual castles changed due to the evolution of real combat devices, i.e. cannons. Trace Italienne are far less interesting / romantic to look at than medieval parapets. But, earthworks are better for defending against cannon balls. I don’t know that giant lumbering structures would prove to be the optimal military strategy. Much would depend upon the nature of magical munitions available, which would also be evolving. In the real world we eventually developed surface to air and air to air missiles. Not to mention nukes. Tea clippers were highly useful for trade even in the age of the steam ship. Not everyone has to be gigantic to make a profit on commerce. Individual control and initiative are important trade factors, especially for small highly valuable goods.


  1. […] essay continues last week’s past, Castles in the Sky Part I: History, Mechanics and Trade.  We covered some history, how the castles mechanically work, and some trade policies.  That […]