[DF] defending a fortress from fliers

[Gnome]

Originally Posted by khorboth

Consider the equivalent of searchlights; a really bright light which can be trained on flyers. Maybe... Roll HT-5 and be blinded for rounds equal to margin of failure. When sight returns, everything except the light source is -5 to target. This will probably be enough time for those on the ground to shoot, cast dispel, position, and do whatever they need to do.

Maybe an illusion only visible from the air? If the defenders aren't powerful enough or don't have enough prep time, it won't be really convincing, but it doesn't really have to be. knowing that it's not an accurate picture doesn't mean you can see what's actually there. So, if it looks like there are no defenders but there really are... then they're hard to target.

The defenders probably have a good idea of what tactically advantageous places to land would be. Those would be great places for traps. Those traps could be ambushes or mechanical or magical or some combination.

If missile shield is a known spell, then it's known that it won't protect against area attacks. Depending upon flight speed, ball lightning can be particularly fun for this application.

What about something designed to make landing areas unattractive? Fake or real patrols, traps, spikes, or archers could force the flyers to land in only a few areas.

Any flying defenders could be accompanied by any number of decoys. A flying fight can be chaotic and anything that makes the attacking force waste resources shooting at illusions or wicker is a bonus.

These are great ideas, thanks! Maybe I'll include a solidly built roof that's covered in traps (or maybe it's one giant trap, like a huge Glue spell or something similar). This could force them to enter through the gate, through one of the few windows, etc.

[VariousRen]

Originally Posted by David Johnston2

Yes. The combination of superior digging ability and the threat from aerial attackers does help explain why the dungeons of dungeon fantasy exist in the first place.

But really if you have a surface installation you want to protect the answer is simple. Anti-air weaponry. Archers and gimbal mounted siege weapons on the walls and towers. And solid roofs on the buildings.

With skill 25 the wizard is likely to maintain Missile Shield (or worse, Reflect Missile!) on the party and render all non-meteoric ranged attacks useless. If their wizard is clever (source: I DM for a clever wizard) they will use Maintain spell on all of these spells before the fight so they only take a -3 from spells on instead of -10. Still worth trying by the defender in case the attacker didn't think of Missile Shield until it was too late, but not the sole strategy to base your defences on.

I always stock my strongholds with a stash of meteoric weaponry to give them some way to hit back against this. It also helps fight back against warriors who have a +4 Shield spell, +2 DB, and +2 Bless. A $30 piece of ammunition negates +8 to their defences.

The other thing to consider are spell arrows. Using quick and dirty enchanting spell arrows can hold any 3 FP or lower spell at a reasonable price ($90 for the enchantment itself, $210 for the gem needed in the arrow). Dispel magic happens to be a 3 FP spell for a 1 hex area. If a stronghold is seriously worried about attackers with significant magical power they could issue every archer an emergency dispel magic arrow. The enchantment itself is relatively cheap at $90, so your elite archers (one or two of your elites should be scouts!) may have dispel magic arrows cast at skill 20, 24, or higher to make absolutely sure they can remove spells from their target. There's a slight problem with hitting the target if they have missile shield, so you may have to wait until they come down to fight and target their hex (an area spell is 4 yards high, so if they fly just high enough to hit someone they will be in range).

Other people have pointed it out already, but I'll second the idea of putting the important stuff underground, or at least include some underground tunnels that connect major buildings so men and supplies can be moved around after the attack starts. You should also be very aware of Destroy Earth and Shape Earth, because they will play havoc with your underground fortress unless you're prepared for them. In my DF game fortresses often have meteoric dust sprinkled into the mortar for stone, rendering it resistant to both spells (though not immune).

A final technique I've used is to make use of summoned creatures, shamanic allies, demon allies, and so on to field forces that naturally fly and can fight the PC's on even footing. A major ghost can make a powerful non-physical threat that can harass attackers in the air. A cleric or appropriately prepared wizard will have spells to deal with it, but a flying fighter will be doomed. Bonus points if you keep these forces in reserve until the PC's are committed and have to figure out on the fly how to fight back against ghosts or flying demons spewing 5d6 cones of fire.

[Gnome]

Originally Posted by Anthony

And in the modern world. Just building DF fortresses in the bunker model is pretty reasonable. The problem is mostly how to combine sensible fortifications with faux-medieval imagery that wants medieval style castles.

Sure, you put static barriers around your fortress to slow or stop land-based attackers. You just don't rely on them.

Ok, that makes sense. Mostly I want it to be an interesting challenge, so if the defenders can offer some external resistance that's good, but if the inside is a dungeon that's good too.

So how do the defenders best defend their fortress/dungeon? This is not your standard DF dungeon, which in my experience is generally composed of mostly separable room encounters; the defenders are a coordinated group, not a grab-bag of monsters.
My first thought is, in a tight space, they can eliminate the flight advantage, but it might be harder for them to leverage their own advantage, which is superior numbers.

[Gnome]

Originally Posted by VariousRen

With skill 25 the wizard is likely to maintain Missile Shield (or worse, Reflect Missile!) on the party and render all non-meteoric ranged attacks useless. If their wizard is clever (source: I DM for a clever wizard) they will use Maintain spell on all of these spells before the fight so they only take a -3 from spells on instead of -10. Still worth trying by the defender in case the attacker didn't think of Missile Shield until it was too late, but not the sole strategy to base your defences on.

I always stock my strongholds with a stash of meteoric weaponry to give them some way to hit back against this. It also helps fight back against warriors who have a +4 Shield spell, +2 DB, and +2 Bless. A $30 piece of ammunition negates +8 to their defences.

The other thing to consider are spell arrows. Using quick and dirty enchanting spell arrows can hold any 3 FP or lower spell at a reasonable price ($90 for the enchantment itself, $210 for the gem needed in the arrow). Dispel magic happens to be a 3 FP spell for a 1 hex area. If a stronghold is seriously worried about attackers with significant magical power they could issue every archer an emergency dispel magic arrow. The enchantment itself is relatively cheap at $90, so your elite archers (one or two of your elites should be scouts!) may have dispel magic arrows cast at skill 20, 24, or higher to make absolutely sure they can remove spells from their target. There's a slight problem with hitting the target if they have missile shield, so you may have to wait until they come down to fight and target their hex (an area spell is 4 yards high, so if they fly just high enough to hit someone they will be in range).

Other people have pointed it out already, but I'll second the idea of putting the important stuff underground, or at least include some underground tunnels that connect major buildings so men and supplies can be moved around after the attack starts. You should also be very aware of Destroy Earth and Shape Earth, because they will play havoc with your underground fortress unless you're prepared for them. In my DF game fortresses often have meteoric dust sprinkled into the mortar for stone, rendering it resistant to both spells (though not immune).

A final technique I've used is to make use of summoned creatures, shamanic allies, demon allies, and so on to field forces that naturally fly and can fight the PC's on even footing. A major ghost can make a powerful non-physical threat that can harass attackers in the air. A cleric or appropriately prepared wizard will have spells to deal with it, but a flying fighter will be doomed. Bonus points if you keep these forces in reserve until the PC's are committed and have to figure out on the fly how to fight back against ghosts or flying demons spewing 5d6 cones of fire.

Great advice here, thanks!

Do meteoric weapons negate the bonus from Bless? It seems to me they wouldn't, since the weapon doesn't interact directly with the Bless.

I like the spell arrow idea a lot. Lots of possibilities for good spells that could enchant these.

The enemy could certainly throw a few allies into the mix (which will get caught in the PC buzzsaw like everything else, but might provide a nice speedbump for the flying part of the fight).

[Anthony]

Originally Posted by Gnome

My first thought is, in a tight space, they can eliminate the flight advantage, but it might be harder for them to leverage their own advantage, which is superior numbers.

The usual method of dealing with this is narrow corridors that open into larger rooms (only one attacker can enter at a time, all defenders can then attack) or kill zones (corridors, ideally with a barrier at the end, that have openings defenders can attack through, but attackers cannot pass through or easily attack through). Traps are also popular, often combined with the above. There are of course also methods for attackers to deal with any of these things (in general CQB methods are pretty applicable to DF).

[Gnome]

Originally Posted by Anthony

The usual method of dealing with this is narrow corridors that open into larger rooms (only one attacker can enter at a time, all defenders can then attack)

With enemies that are so much weaker than the PCs, I worry the PCs could just send spells, explosive missiles, creations, etc. through the door to decimate the enemy before they're even engaged.

or kill zones (corridors, ideally with a barrier at the end, that have openings defenders can attack through, but attackers cannot pass through or easily attack through).

That's a good idea I have to consider. How do I get them to enter the kill zone though? They can use worthless creations to scout any area that looks dangerous...

Traps are also popular, often combined with the above. There are of course also methods for attackers to deal with any of these things (in general CQB methods are pretty applicable to DF).

I think I need to invent some "smart" traps (probably magical) that can't easily be triggered by those same creations.
This is a nice framework to get me thinking about this, thanks! I don't have any real-world tactical experience, so I'm not familiar with CQB methods, but I think I understand your suggestions. I think I still need help nailing down the specifics though if you have more ideas...

[VariousRen]

Originally Posted by Gnome

Great advice here, thanks!

Do meteoric weapons negate the bonus from Bless? It seems to me they wouldn't, since the weapon doesn't interact directly with the Bless.

It will likely vary from game to game depending on how your DM interprets the meteoric effect. Our group plays with meteoric weapons being "invisible" to magic, which includes divine magic like bless. Bless (and Deflect, Shield, Armour, and Fortify) all rely on magic to notice that the weapon is incoming and actively resist it. A meteoric weapon is never "seen" and passes right through the magical defences.

On the other side of things magic that affects the person rather than the weapon doesn't care about meteoric weapons. Haste makes the person faster, so they can still dodge meteoric weapons with a bonus. Body of Air literally turns you into air, so a meteoric crossbow bolt will pass through without doing much at all.

This interpretation has worked pretty well for my group and avoided any serious problems with figuring out what meteoric affects and what it doesn't. There are plenty of borderline cases though, so like I said it will depend on the DM. Another reasonable interpretation for Bless, for example, might give it's flat bonus to your defences (because you are just better at everything while blessed) but not avoid a critical disaster (because your god doesn't see it coming).

[David Johnston2]

Originally Posted by VariousRen

It will likely vary from game to game depending on how your DM interprets the meteoric effect. Our group plays with meteoric weapons being "invisible" to magic, which includes divine magic like bless. Bless (and Deflect, Shield, Armour, and Fortify) .

Hunh. I would have expected meteoric iron to ignore arcane magic but not divine magic.

[Apollonian]

Originally Posted by Gnome

The PCs (500-700 point delvers) are about to assault a well-defended human-built fortress. The assaulting party has a caster with Flight-25 who can cast and maintain Flight on the entire party, as well as Missile Shield if need be. He can also create any number of relatively weakish allies with Create Animal. Between the two of them, the PC casters can cast a large number of other relevant spells: Windstorm, Lightning, Concussion, Great Haste, Deflect Missile, and many more. It seems to me likely (but not certain) that they will try an aerial approach, at least if it seems possible to do so.

The defenders should be well-prepared for any sort of attack, including this one or an assault by a large ground force, a small elite force, a dragon, a demon, a mindwarper etc. They have ~100 soldiers (well-equipped and indluding some low-level casters, skills generally around 16) and 5-10 "elite" defenders (warriors with skill levels in the high 20s and casters with skills levels around 20).

So what should the defenders' strategy be? How should the fortress be constructed to be ready to defend against a diverse set of fantasy threats? What kinds of spells/abilities should the defenders have available to make this a challenging encounter? Does anyone have any awesome ideas for fantasy siege weapons that fit well into "DF-world"?
Any other ideas as to how I can make this encounter awesome?

One thing to think about is: Of all the available countermeasures and defenses, which ones should PCs be able to find out about or expect because they're standard practice in the setting, and which ones should be nasty surprises?

"Like most fortresses, Stalag-23 is ringed with anti-air and anti-magic defenses. They have the gold to fund some good stuff, so we should expect to encounter at least one null-magic field above the fortress and meteoric mortar to slow stone shaping. Thanks to Ranald's scouting efforts, we know that they have watchposts circling the fortress; these posts are manned by regular soldiers and a few animal control specialists, so we should assume that any crows or squirrels in the surroundings could be enemy eyes.

The gate is enchanted heavily to resist practically anything. We suspect that an earth elemental is bound to western tower, but we're not sure. If so, it'll be like that place out in East Adria. There should be a postern gate or underground entrance, but we haven't found it on our initial scouting. It's probably disguised; maybe with magic, maybe not.

On the walls, they have the usual complement of ballistae and catapults, plus a few of those dwarven multi-bolt crossbow... things. Deflect Missile should make those a non-issue; we don't think they have enough gold to equip it all with meteoric projectiles."

And so on.

Does the garrison expect the PCs in particular to be an enemy? If so, they should have worked out some specific countermeasures to what they know about the PCs, especially if the PCs have a particular flashy schtick or something that would be known to observers.

If you really want to mix things up, have a third party act under the confusion caused by the PCs assault, or clue the PCs in that a third party will be assaulting and they can use that for cover or as a distraction.

Also, very few fortresses are expected to stand alone. Where will a relief force come from, and how long will it take to get there? Knowing about this will give the PCs some time pressure.

[Anthony]

Originally Posted by Gnome

That's a good idea I have to consider. How do I get them to enter the kill zone though? They can use worthless creations to scout any area that looks dangerous...

Because the kill zone is the entrance? You put your defenses where your opponents need to go.

As far as scouting with worthless creations, I assume there's something more to it that just create animal? Creations do not inherently reveal what they see to their caster, and created animals have animal intelligence. Also, the usual solution to scouts is killing them.