When I started creating my high fantasy world of Macalgra, I stumbled onto a serious issue very early. I went into things with the intention of creating a medieval world (spoiler: it didn’t happen). But I’d created a magic system that rendered the classic staples of a medieval world defunct. Plate armor, knights on horseback, stone castles – all the things that scream “medieval” – were totally useless with magic.
The reality is castles don’t make sense in high fantasy.
Castles can be torn down by magic
In a classic medieval world, you imagine castles. But just as cannons made castles obsolete, magic does something similar. Fireballs, earthbending, teleportation and many other forms of magic can easily destroy or circumvent a castle.
One alternative is earthen Star Forts. This style of fortification came into use when cannons began to be mass produced. A Star Fort consists of multiple, overlapping angled earthen walls, with the keep and other important buildings at the center. The whole compound may also be surrounded by a moat.
Against mages, a similar structure could provide cushioning from magical barrage. It would also allow your mages to cover all approaches to the compound and fire back.
Dragons can fly over castle walls
Game of Thrones addresses this problem as one of its central conflicts. Dragons can simply fly over a castle wall, and star forts might be even more vulnerable. There would be no heavy stone walls to hide behind when a dragon lands in the middle of your castle.
Hiding in your castle would also be difficult if Dwarves could use their subterranean engineering to tunnel under a castle walls. Other species may bring their own unique problem to fortifying strongholds.
Plate armor is a hindrance
Expensive plate armor is practically pointless. A mage can heat it up and cook you inside, possess your armor and crush you with it, or wish it out of existence. This type of armour is hard to produce at the best of times, and the protection it offers against arrows and swords is less important than what it can do against magic.
The ancient Greeks used the Linothorax, and it honestly has some benefits in an ancient world magic-setting. In a medieval setting, the gambeson is similarly useful.
The linothorax is made of linen, which is an astoundingly resilient material. It is lighter than bronze armor, and has less tendency to overheat the wearer marching in the sun. It also is less prone to boiling you if a mage decides to heat up all the nearby metal.
Linen is a lot cheaper than bronze or iron. Killing a soldier wearing linen armour with magic would still be possible but metal would offer no extra protection and simply cost more.
Think about what mages can do
When considering how your soldiers would arm themselves, think about what your mage can do. If your magic is about throwing fireballs, large shields with fire retardant coverings might be a good option. But if your magic involves elemental sorcery (geomancy, pyromancy etc), such as in Avatar the Last Airbender, then you may have to avoid the materials that your enemy’s mages can manipulate.
If special materials can block magic, then these would make perfect armor. Or your magic system might allow for protective warding on armor.
Magical shields and force-fields
If your magic system allows for force-fields and shields, fortifications are probably more magical than they are physical. With the right mages, you could defend anything – an unfortified city could be covered by a shield to repel attackers.
But this doesn’t mean fortifications are totally off the playing field. As in Harry Potter, your shield may be short-term and it may only be the first level of a fortress. A shield could potentially be useful for depleting the enemy mages and forcing the foot soldiers to attack you. Therefore, having good fortifications after the shield goes down is still a life saver.
In conclusion, consider it early
It is critical to think about how your magic works in a martial capacity. It potentially changes the entire setting. Both the social orders and architecture of the medieval period was dictated by the military technology of the time. If your world’s military can harness magic, this changes the face of cities, government and seats of power.
Check out my questionnaire for developing magic for more points to think about when creating magic systems. I also recommend Shadiversity‘s video on this topic for some great ways you could adapt castles to magic.