When I started creating my high fantasy world, I stumbled onto a serious issue very early. I went into things with the intention of creating a classic 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 always make sense in a lot of 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.
The point of a castle is to sustain a long, protracted siege – in essence, to make it too expensive to conquer a place unless you really want it. Fantasy movies often show grand, action packed assaults on castles, but besieging was often a much slower, sometimes months long process in the real world.
While magic could offer some benefits to the defenders of a castle (magic could perhaps pureify putrid water, heal wounds and provide heat when fuel runs low), it also gives the attackers numerous advantages.
In the real world, one of the methods used to assault a castle was to undermine the walls. If your world had an earth mage who can bend stone, this weeks long process could be achieved in a day. Another method was to make the defenders too weak to hold the walls, whether from starvation, poisoning their water or throwing dead animals over the walls to spread disease. If we look at a magic system like D&D, there are numerous spells that could poison or disease a static defending force, unless they had their own equally powerful mages.
Finally, you have the most obvious method – assaulting the walls with projectiles. In the real world, this was achieved with expensive, slow moving and vulnerable catapults and trebuchets. But fireballs, a staple of many magic systems, only require feeding a single mage instead of a team of siege engineers, can move a whole lot faster, and don’t need to be reloaded with large boulders. Their effect on siege warfare could perhaps look similar to cannons.
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 from fireballs. The earthen walls take the hit, instead of the stonework. It would also allow your mages to cover all approaches to the compound and fire back. Star forts have less blind spots than traditional castles. However, they’re not an answer to all castle’s woes in fantasy.
Dragons can fly over castle walls
Game of Thrones (A Song of Ice and Fire) 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. Game of Throne’s response to this question is that dragons are so rare (and by the time of the books and show, nearly extinct) that even though they provide a massive destabilizing influence and can easily defeat castles, they haven’t completely made castles obsolete because of their small numbers.
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. For example, giants could tear down fortifications by hand or simply step over the walls of a star fort.
Plate armor might be a hindrance
Expensive plate armor in the real world is meant to stop swords and arrows. Yet in fantasy, it faces new challenges. This type of armour is hard to produce at the best of times, and the protection it offers against arrows and swords might be less important than what it can do against magic.
Elemental manipulation is a common ability in fantasy, and if it exists, a mage could heat up your armor and cook you inside, possess your armor and crush you with it, or wish it out of existence.
An alternative exists however. 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 or iron 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. It provides possibly superior protection from arrows, and potentially could be better against fireballs and other projectile spells.
In addition, linen is a lot cheaper than bronze or iron. Killing a soldier wearing linen armour with magic would still be possible but the added protection of metal might be limited and it simply costs 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.
But if shields are very powerful, you might be better having lots of mages specialising in shield magic than expending them on fireballs and offensive magic.
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.