Castle Defenses

[Loincloth of Armour]

In my campaigns places like castles and forts are allowed to get magic defenses at reduced costs. After all, in a world with magic it’s as silly to build a fort without considering magic assault as it is to build a fort with only 3 out of 4 walls.

So I include things like scry blockers and summon monster traps that activate upon unauthorized teleports and the like. Basically, the castle designers have access to the PHB and its spells and have set out thaumaturgical defenses against common spell and spell caster tactics.

For permanent structures I slightly bend the rules regarding the defensive spell’s abilities, while keeping to the spirit of the spell’s effects.

Unfortunately, in defending against one specific part, I acknowledge I’ve created a problem, and wish to plug it.

The idea is not to punish my players: if they can think of something new and cool, that’s fine. But if I can think of the idea, then the mages/clerics responsible for assisting castle protection should have thought up defenses for it.



The problem is my defenses against the “flying, invisible” or the “wild shaped into a bird” invader. What I usually place over castles is something akin to a wall of greater dispel magic, shaped like a hemisphere with a base at the top of the castle wall and peaking above the central keep. This is a basic security device, designed to inhibit (not necessarily just prevent), anyone from just flying over. You cross over and there’s a good chance your invisibility, flight, or shape-shifting magic gets cancelled, dropping you down and letting people know you’re there. It also has the added bonus of keeping down the instances of mages doing the whole, “Greater invisibility and fireballing the castle wall from 400+ feet away” situation.

The problem is that with this set up, I know someone will take a bunch of boulders, cast shrink item on them, and then fly above the castle and drop them. Boulders hit the dispel magic field, turn back to their real size, and crash down to cause damage.

I have no problem with the flying overhead with boulders idea, I use air forces of mounted griffons and hippogriffs to deal with fliers, but I’m looking for a way to deal with the shrink item issue.

I’m thinking of a wide area mage hand effect, just above the dispel magic dome. Anything non-living that weighs less than 5 pounds that is falling towards the castle get mage handed and flung outside the castle walls. This won’t affect regular birds and such, and rain won’t be affected (although it might help against natural hail damage as a side affect).

Anyone have other (preferably low level magic) ideas on how to defend against the “shrink the boulders” concept?

 

[Pyrex]

Well, it depends on how much your ruler wants to spend on defense.

First replace the 'Dome of Dispel Magic' with a dome-shaped Wall of Force large enough go cover your castle. Then surround the entire dome with an Antimagic Field.

If you really want to amp up the defense, use a Prismatic (hemi)Sphere instead of your dome of Force inside the Antimagic Field

 

[Shayuri]

Just tough it out?

It's no worse than catapults and trebuchets firing blocks of stone, really. And whoever's flinging the boulders is probably even more vulnerable to return fire than field artillery would be.

Or adapt a version of Repel Wood, and Repel Metal.

Repel Stone! Why not? It'd even work on siege machinery.

Course, then they drop metal blocks...but those get spency. And you can use Repel Metal.

 

[Loincloth of Armour]

First replace the 'Dome of Dispel Magic' with a dome-shaped Wall of Force large enough go cover your castle. Then surround the entire dome with an Antimagic Field.

If you really want to amp up the defense, use a Prismatic (hemi)Sphere instead of your dome of Force inside the Antimagic Field

I did say magic defenses were at a "reduced cost", but I also said "preferably low level magic."

I could shift the whole castle into the etheral plane if we're going that far. But I'm not. I'm looking for simple, reasonable defenses that offer players the chance to be effective, not simply tell the mage, "Sorry, all your spells and class features are useless. Thanks for playing."

Not to mention what the Prismatic Sphere's blindness effects would do the 1-8th level warriors who man the wall....

Just tough it out?

It's no worse than catapults and trebuchets firing blocks of stone, really. And whoever's flinging the boulders is probably even more vulnerable to return fire than field artillery would be.

It is worse, because setting up catapults and trebuchets within attacking distance of a castle takes time, effort, and a usually very visible army that tends to attract a lot of attention.

One PC with Greater Invisibility, Fly, and a few days to use all his 3+ level spell slots for Reduce Item shouldn't be able to decimate a fortress by himself. Mages are powerful, not gods.

And... I kind of want to promote seiges as effective battle plans. Reduce (not eliminate) the effectiveness of magic on taking out fortified structures, but also tell the old, "We're safe, so long as our walls remain unbreached," kind of stories.

Or adapt a version of Repel Wood, and Repel Metal.

Repel Stone! Why not? It'd even work on siege machinery.

Course, then they drop metal blocks...but those get spency. And you can use Repel Metal.

Excellent! That's the kind of thing I'm looking for. Simple, effective, and involves unique applications of relatively low-power spells without being overkill.

Not to mention the fun of seeing the seige commander saying, "What do you mean our rocks are being tossed back at us?"

edit: Hmm... I like the idea, but a quick check turns out that Repel Metal or Stone is Drd 8. I'd prefer something in the 1-4th spell levels.

 

[Shayuri]

Arr...just beware of workarounds!

Polymorph Any Object is renowned for it's potential to turn stones into Adamantine.

Granted...high level. But at a much more accessible level, Major Creation can make short-lived adamantine blocks. If they have Repel Metal, expect players to get sneaky.

Glass, for example. Is it stone? How about ice? A bunch of rust monsters all bundled together with twine? Catapults can fling -anything-.

Edit - That's pretty tricky. You could counter invisibility fairly easily with a See Invisible effect, or Invisibility Purge. Countering shrunken item flingers is harder with low level spells. One possible nerf of the Shrink Item spell is to say that the energy is conserved. That is, a wizard with Strength 9 flings the pebbles...but when they become boulders they're treated as if they'd been flung with Strength 9 at their new mass. Doesn't help with dropping them, granted.

Hmm. Maybe some kind of Resiliant Sphere trap that automatically targets anything breaking a particular radius (perhaps an Alarm spell is linked to it)... Or a generic Repulsion effect...though that's high level again. Take a page from Return to the Temple of Elemental Evil and have towers that see invisible and automatically spit 10d6 lightning bolts at anything that flies within 150'?

 

[Shayuri]

You know whaat might work? Reverse Gravity field above the castle.

Yeah yeah, it's high level, but oh-so convenient, and it would provide nearly flawless protection against ANY ballistic attack...even artillery typically drops the rocks from above on ballistic arcs. Such a castle would be VERY well protected!

 

[RangerWickett]

A fantasy war is like a modern war.

People don't build castles anymore. They build bunkers.

 

[Loincloth of Armour]

Arr...just beware of workarounds!

I got no problems with workarounds. What I want to see is:

Players: Attacking a castle is easy. I don't know why anyone builds them. We cast ABC.

Me (the DM): [checks notes] Turns out they thought of that long ago. Your magic ABC is met by magic XYZ and countered.

Players: *&%#!! Okay... give us a few minutes... [talk among themselves]. Now we try Plan B.

Me (the DM): [thinks for a moment] Yeah, that's clever and unusual. That'll work.

My NPCs aren't idiots, but they're not all knowing either. If the players come up with truly creative ideas, I'll reward them.

But I do want to promote seige conflicts (and commando raids during seiges and surgical strikes, etc), so that's why I'm looking for ways to defend castles from magic.

Take a page from Return to the Temple of Elemental Evil and have towers that see invisible and automatically spit 10d6 lightning bolts at anything that flies within 150'?

Yeah, the lords and such of my worlds have 'no fly zones' over their castles as well. Magic seige engines with anti-aircraft capacity and air cavalry of griffins and hippogriffs deals with the regular fantasy flying threats (dragons, et al) fairly well.

A fantasy war is like a modern war.

People don't build castles anymore. They build bunkers.

And with a bit of magic defenses in play, fantasy war once more approaches RotK style. It becomes a blend of aeral assault and specalizied commando teams mixed with knightly cavalry charges and medevial seiges. That's what I'm aiming for.

 

[Tonguez]

I think Castles in a fantasy world will be about Ostentation rather than defense, the defensive structures will move underground and be magically warded, what you see on the surface will be a lavish facade designed to impress the common folk (and adventurers) into acknowledging that the Lord of the Keep is powerful and has extensive resources at their disposal.

This might mean that castles are carved into cliffsides on in caves (with the functional sections inside the cliff/mountain)

of course that gives vunerability to eathquakes and earth elementals...

 

[Gerion of Mercadia]

ok -

1. Invisibility purge. Fliers that can't be seen are annoying. VERY annoying.

2. Glitterdust clouds. This tactic not only deals with non-magical hiders, but also outlines the invisible ones.

3. Archers and/or ballistae that have "True Strike" capability - that may or may not be firing magical ammunition.

EDIT: Added to wrong post - whoops