How does a fortress defend from magical attacks?

[Disciple Cain]

The best defense is a good offense. Kill the mage and your problem is solved. Deal with mages like you deal with siege weapons-- destroy them or disable them by any available means before they can do any serious damage. How you can do that depends on how mages work, however, and the given resources at your disposal.

[Assallya]

Much of this is dependant on the magicians in your realm. In D&D for example, there is no spell that actually will do the job. Even "rock to mud" holds the cause that it only is effective against "unworked stone".

For the most part, advanced intelligence is the best defense against magic. Scry your enemies as best as possible, cast runes or bones to foretell the future. Whatever it takes. Also ensure nobody walks off with a bit of your castle wall. Your enemies could build a miniature version of the castle using that small bit of the wall you stole and you have a sympathetic link for magical rituals allowing you to cast spells against the wall from hundreds of miles away!

In many cases, those without magic of their own, may still use magic through evocation in the form of ritual, sacrifice, or crafting. By introducing proper runes or symbols into the stonework mere mortals could evoke the force of a god, demon, or something more elemental to empower the bulwarks to resist such attacks.

Additionally, one might have magic resistant materials occurring naturally in the world. Maybe its certain stones, maybe it involves a special metallic ornamentation or perhaps just infusing the mortar between the stones with certain herbs might do the trick.

You could also bind spirits, like a Djinn or a greater demon and force it to patrol the castle astrally and ensure nobody tries anything nasty without it being counterspelled and the local magicians being informed.

[Foster]

Mana-void, nullification-zones, and cursed/holy-ground.

[Knighthawk]

This is almost all D&D based information:

Lead. Lead sheets have been used to protect from scrying attempts as thin as a 'sheet' less then one inch thick. Protect your important rooms from scrying with lead plates.

Cold iron. Often times cold iron is used to harm magical creatures or bind mages so that they may not cast spells.

Illusions. "Misdirection. What the eyes see and the ears hear, the mind believes." Both magical and mundane methods to protect from scrying and targeting.

Magic. "Only magic can defeat magic."-Uncle Counter spells, counter-casters. if you are using D&D then abjuration does wonders.

Terrain. Position the earth itself so that they have to expose themselves to cast effectively then snipe them with a catapult.

[GrievousKhan]

The truth is there is no real way, or at least not any none expensive way, to insure a fortress or strong hold is magic proof.

Your best solution does stem from something often used in D&D but is quite overlooked. And that thing are dungeons, as traditional castles and other strongholds are harder to defend, especially against an enemies who can fly, teleport, and or use magic to turn your fortress walls to mud.

Thus, underground strongholds (dungeons, in other words) are your best bet, you wont find anything better really, because they can't be attacked from above and enemies who don;t know their layouts can't teleport into them.

And enemies are more easily out flanked if they unknowingly march over their enemy army.

Dungeons are your best bet.

[Assallya]

What would be good is if we knew what particular magical system we were contending with. It would allow us to greatly narrow what is essentially an area of infinite probability.

*grins* After all, if we're talking Hyborean era magic than just about all structures, even log cabins, are fairly safe

[Ellri]

yes, it all depends on which magic system is being used, and how it works.

[Omega]

Enchant it to be magic resistant.

[GrievousKhan]

Oh, he is talking about D&D.

Know how I know this?

Because Google is my Bitch.

[MelonHead]

The truth is there is no real way, or at least not any none expensive way, to insure a fortress or strong hold is magic proof.

Your best solution does stem from something often used in D&D but is quite overlooked. And that thing are dungeons, as traditional castles and other strongholds are harder to defend, especially against an enemies who can fly, teleport, and or use magic to turn your fortress walls to mud.

Thus, underground strongholds (dungeons, in other words) are your best bet, you wont find anything better really, because they can't be attacked from above and enemies who don;t know their layouts can't teleport into them.

And enemies are more easily out flanked if they unknowingly march over their enemy army.

Dungeons are your best bet.

You know a lot about DnD Khan, but you evidently fail to understand the point of a castle.

A dungeon would completely and utterly defeat the point of a castle.