Allow me to shed some light on this subject (turns on lightbulb).

Brief Overview of Magic

These powers manifest themselves any time from birth to the end of puberty. These magical powers fall under seven broad categories. Air, water, earth, plasma (fire/lightning), plants, light, and animals. Animal magic is tricky, because living things resist magic. But, many animal mages can influence animals, and some can control dead animals (this is called necromancy and is a big societal no-no.) The strength and scope of magic varies from individual to individual. But, these are the most common in order. Earth, water, air, plants, animals, plasma, and light.

These magical capabilities are like the show Avatar, the Last Airbender, in how controlling magic works. However, in my book magic is much less powerful. For instance, an earth Mage may only be able to influence as much dirt as they could lift, and lifting this dirt would take about as much energy as doing it by hand, except you don't have to touch it, and it could be a perfect brick shape. No force is exerted in separating the dirt or material from other similar material attached to it. So if you were to pull this rock in two, that would take little effort, other than the force of pushing the pieces apart.

Magic is like a muscle that is really hard to develop.

Magic on a larger scale

The level of magic described above is only about 75% of magic users. Everyone else is more powerful.The strongest people can do things like shoot lasers, uproot trees, be human flame throwers, make zombie hordes, create small tornadoes, cause rovers to overflow or to break dams, or cause small earthquakes. This is about 7% of the population. Everyone else is in between.

Magic on a smaller scale

I'll just make a list of some possible fighting applications of magic. Ice daggers, water whips, wind influenced arrows, starting fires, shooting small fireballs, throwing stones, moving stones, strangling people with vines, tripping up enemies with plants, scaring/exciting horses, and flashing people. (With lights!) These are of course by no means the only applications of magic.

Magic Resistance

Living things are resistant to magic, proportional to their intelligence/self awareness. So it would be easiest to make a swarm of spiders, then harder to make boars attack (your enemies, and not yourself), and nearly impossible to make someone slap themself. There is a type of stone resistant to magical tampering, which is found deep underground, near bedrock. Also, bones are immune to magic.

Note - These things are resistant to magic being influenced directly upon it, not magically influenced material. A rock thrown by magic at someone is just as effective as a rock thrown without magic at the same speed.

Now that You've heard me drone on and on, let's get back to the original question. With magical abilities such as these, how would the architecture and design of castles change to combat these threats? Would castles even be practical?


I feel like I need to excuse myself in advance, this answer got quite long, but I hope it contains some valuable Ideas for you.

A stone castle by it self as we know them would be rather unlikey, because an attacker could simply tear the walls aparty bit by bit. So, what are alternatives? Let's have a short think on what requirements (note: source is in german!) a castle needs to fulfill:

  • be protective: This is the most important requirement, as protecting the castles lord and his followers from attacks is the essential reason of building a castle
  • be scaring: A castle was an important way of frightening enemies to not even make them think about attacking
  • be secureable: Castles were also used as prisons, to hold enemies or criminals captive
  • be impressive: Another reason of having a castle would be to show wealth and superiority.

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Real-world castles do very well on this requirements, as common technology during that time could not seriously threaten them. With the invention of gunpowder, this changed over time and the protection they offered shrank. People stopped building castles as all of us know. But in a world that contained magic the way you described, such a classic castle would not do well in the first place:

  • The protection aspect would be nearly gone, as (like described) stone walls could be easily degraded bit by bit from afar. Highly magic powered people are very common in your scenario: with a rate of 7% it would be easy for an evil army to gather some master mages that would tear down a wall in seconds
  • Considered this danger, the scariness of a castle vanishes quite fast.
  • securability is also gone, for obvious reasons
  • being so easily destroyable, such a castle loses a lot of its impressiveness

As we have seen, classic castles won't do very well in a magic setting, so which would?

The main problem that is to solve is finding a material, that is both well resistant to magic and easily obtainable, as you need a lot of it to build a big structure that can hold such a lot of people. The first and currently only material that comes to my mind is metal. Fire (or plasma) is the second least common manifestation of magic in your world, and even for those capable of it, a basic fireball isn't of much use against a metal plated castle wall. So by plating your walls with iron, you have some good protection against magic, and it is also quite shiny and impressive. Plating a whole castle in metal would be very expensive though, which makes this solution hard to implement.

Another possibility of protection is building your castle underground (This post might help on that). Building an underground castle would be cheaper than plating that whole thing with iron - but it is still very difficult to construct (again, read the linked post, it seems interesting). Placement in general is a very important factor in this scenario. Building your castle on a very high mountain, or in the middle of a large lake both improve the protection that your castle offers to you and is also quite impressive!

But after all, I think there is no way to fully and reliably protect and secure your castle in a world with such a lot of (often times powerful) magicians. So I would not go for a standard castle, but throw away my goal of impressiveness and focus on two main aspects:

  • secrecy and
  • combat power

Keeping the location of my most important ressources and hideouts secret is one of the best ways to protect yourself from enemy attacks. If my enemy does not know where I am, he can not hurt me.

This works on small to medium scale and is useful to protect the most important persons or my most valued treasure. It is also usefull for protecting small groups of houses. But hiding a castles worth of people is a difficult if not impossible task, for which I guess the best and most effective strategy here is combat power.

Instead of solely relying on the passive protection that medieval castles used to offer, I would bet on an offensive setup:

  • train my warriors and magicians to improve their powers to a maximum
  • improve my (probably quite classicaly medieval-looking) castle with offensive builds, for example:

    • Ranged weapon systems on towers
    • traps. Loads and loads of traps.
    • Underground tunnels leading from within the castle to the outside, to attack the enemy from behind
    • ...

In conclusion, my bet would be to follow the old wisdom: Offense is the best defense and I would do anything for my castle to support this attitude.

Edit: Wow! I totally missed your point on how bones resist magic in the first place! They are a cheaper alternative to iron, but serve the same purpose. They are, of course, easier to destroy by normal means, but get creative! Imagine a castle, covered with the bones of your slain foes, casted into iron and crafted into a huge metal wall of bones! How badass is this? Your enemy will be absolutely terrified! This, combined with the already mentioned ideas would form a pretty well solution, I guess.

Possibly interesting further reads:

  • $\begingroup$ I approve of this answer, it is detailed and addresses the question nicely. However, One thing I think I will change is that there is about 3% that have the ability to nullify magic. Also, two magicians attempting to influence the same area/thing/piece of material, with one not being much more powerful than the other, could prevent either from working their magic. $\endgroup$ – Xandar The Zenon Jan 17 '16 at 19:31
  • $\begingroup$ Thank you. I would guess, that such a change would basically lead to an increased staff of guardsmen, preferrably those "nullifyers", so they can prevent foes from using magic for attacks. You might wanna protect them well, though, as they would be an important target for attackers. Disabeling the mages leaves you with a "classic" army to deal with, providing castles as we know them with the comeback they deserve :) $\endgroup$ – T3 H40 Jan 18 '16 at 7:57
  • $\begingroup$ Yeah, but probably less arrow holes and things like that. My main character is a nullifyer, but when put under duress he finds that he can use different types of magic (not at once). $\endgroup$ – Xandar The Zenon Jan 18 '16 at 17:22
  • $\begingroup$ Sounds like a pretty solid idea! I just added a short segment on the use of bones. I totally missed that in the first place - thanks to @NicolasPierre for pointing them out, he has some nice points! $\endgroup$ – T3 H40 Jan 18 '16 at 18:14
  • $\begingroup$ doesn't have to be the bones of your enemies - not necessarily enough of those around. Livestock bones on the other hand are a lot more plentiful. Also of potential is your ancestors. Bones could be retained for this purpose... $\endgroup$ – Baldrickk Nov 2 '17 at 13:30

Bone labyrinth all the way !

Some explanations are in order : as your enemy has 7% high powered magic users, so do you.

Bone covered walls would be hard to directly affect and would need physical ranged attacks to be affected. The covering could be a paint or bone powder in the mortar, for example. With intelligent being bones more efficient than "lower life forms. The remaining attacks would provide threat similar to siege weapons, except in the few and far case of extremely powerful magic user that your own magic users could target, protected by your walls.

Another way of coping with the high threat magic user would be through advanced guards posts, designed to stay hidden and only act once the enemy army has taken camp to eliminate the invaders' leaders.

In case this fails, turn the city inside the walls into a labyrinth with bone-laced walls where your common soldiers will have an easier time fighting in a known environment.

So : classical castle / fortified city with bone laced walls and advanced stealthy guard post to take care of the few individual that present real threat to your army.

It is to be noted that very few castle were taken by brute strength alone. Treachery, hunger, disease and a couple of duels were far more efficient.

  • $\begingroup$ Someone needs to take a visit to Paris. I'll definitely add a bone labyrinth, or a castle made out of cement with bone fragments. $\endgroup$ – Xandar The Zenon Jan 18 '16 at 17:30
  • $\begingroup$ For inspiration, take a look at Piers Anthony's Book of Xanth (The blue Adept might also be of interest) and the comic "Lanfeust of Troy" - I'm not sure of the English titles, not even sure the comic is translated - They seem to touch your subject. $\endgroup$ – MakorDal Jan 18 '16 at 19:34

As described by @T3H40, the traditional castle is useless in magical combat situations, so what we need to work out is why the ubiquitous mage tower came to be and what it's advantages are.

Towers have certain features in common with castles.

  • Statement of power
  • Visible from a wide area
  • Visibility over a wide area
  • Able to exert power over a road, port or town

The mage tower has one specific advantage that castles don't but a mage in a castle still has.

  • The tower gives good line of sight for use of magical abilities with no practical limit on range

These are statements of power over population, not power relative to another holder of power. (For those in the UK, this series is really good).

The majority of the castles in the UK were built as statements as much as positions of power. While they were capable of being used as such, their actual practical life as fortresses was not long. From the first castles in the UK after 1066 to the point where Robert the Bruce realised that it was better to pull them down than keep them just over 200 years later.

There's going to be a short period coming out of the darkness when mages will become lords of the land. (The simple definition of a ruler being someone who has the power to protect themselves and the people around them from another who wishes to rule.)

Sometimes these will be the mages taking power for themselves, sometimes the people will be going to the mage to ask for protection from raiders and bandits. These little princedoms start as being the area visible from the top of their tower, it's going to take power to build a tower. The bigger the tower, the more powerful the mage, the larger the area of control. The larger the area of control the more the tribute and taxes will roll in. The richer and more powerful the mage the more money and power they want. Lords will become princes, princes will become kings, ruling without armies, simply by the power of their own hand. The powerful will accept the subservience of the weak. Those with some power will serve those with a lot, kingdoms grow by subservient dukes with the towers growing across the land as the symbol of the power of the mages over the people.

Mage towers don't have to defend against mages, in the same way that castles rarely had to defend against kings. It's only once the mage wars kick off properly that you'll have to start considering defence against other mages rather than just the usual stone defences against armed men, requiring them only to be slowed enough for the mage in the tower to kill them all.

Once the mage wars start, the towers in disputed areas will be pulled down instead of captured and armies will be formed as cover for mages on the move. The simplest way to defend a person being anonymity in the crowd.

The towers in safer areas and large cities will remain, they are still the greatest statement of the power of a mage over the surrounding area.

  • $\begingroup$ Towers would be good, especially for underground structures. That way, they know when they're being attacked and can defend easily. $\endgroup$ – Xandar The Zenon Jan 18 '16 at 17:31

I think a critical point in your description is this "Living things are resistant to magic, proportional to their intelligence/self awareness.".

The key to visible, effective defences then becomes not what they're made of but how to imbue them with "livingness". The details of this path depend on the mechanics of your magic system but when I designed a fantasy world I found good direction from the rules on binding souls into items. Interestingly enough, some of the ways to bind a soul to a wall involve sacrificing victims in the foundations, a practice strangely present in the real world (http://nzetc.victoria.ac.nz/tm/scholarly/tei-Bes01Reli-t1-body-d5-d2-d2.html).

The second part of your sentence ("proportional to their intelligence/self awareness") gets even more entertaining as it means that there's little value in sacrificing the closest labourer - you want to hunt down a few powerful mages and bury them under the foundation stone to make your fortress stronger.

Of course sacrifice isn't the only approach. My rules allowed a mage to focus their life essence into a structure so when a castle was under attack the defenders inside would include mages touching the walls and resisting the magical attacks focussed on those walls. A mage could also voluntarily bind their essence to a structure as they died.

My rules on binding stripped most intelligence away leaving just the basic life essence but that essence would retain characteristics of the original person so a fortress strengthened by the soul of an evil person would retain that cold, dark nature and a homestead protected by the spirit of a long-dead druid would feel balanced, calm and protective. Your rules, of course, might be different but you can see that this opens many useful doors for world design and story-telling.

In addition to that I tended to carve castles from the internals of natural stone features jutting out over a pass or above an area to be controlled or protected. That wasn't so much to protect from magic as because the ability to drop heavy objects from above completely changes the structural strength required from buildings. This construction approach is generally impractical in our world but when you can carve stone like butter it becomes fast and easy. It also gives these castles a distinctive look and feel (I must post some pictures of my old world online sometime).

Hope this provides food for thought.

  • $\begingroup$ A very good answer. However, I'm avoiding things relating to souls and the afterlife in my book, so I don't think I'll use it. You also made me imagine a castle with walls made out of sheep, which I found pretty amusing. :) $\endgroup$ – Xandar The Zenon Jan 18 '16 at 17:29
  • $\begingroup$ The sheep wall idea was hilarious but you've reminded me that it doesn't have to be souls - would living plants resist magic in the same way? $\endgroup$ – christutty Jan 20 '16 at 3:11
  • $\begingroup$ Well, plant wizards can control plants, so they could make them move when alive. Think trees waving their branches, or ivy curling around people's legs. Once dead, it becomes like influencing earth. So they would provide at least a little protection. But plants do burn, so watch out for that. $\endgroup$ – Xandar The Zenon Jan 20 '16 at 3:15

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