Foiling knock spells

[MarauderX]

Trap the door. Trap it with something like, say... dispel magic? If I were an NPC and doors weren't holding my enemy back, I would trap the other side of the door so that once a character was inside he had to also know to jump over the first 5' beyond the door.

 

[Someone]

Make the door have a mechanism -magical or mundane- that closes it inmediately as soon it´s open unless you pick the lock (or use the key)

 

[Pielorinho]

Two locks per door.

One lock (randomly chosen per door), when unlocked, opens the door.

The other lock, when unlocked, opens a pit trap in front of the door. Or sets off an alarm. Or opens the door but releases an odorless, poisonous gas around the door. Or causes metal bars to fall into slots in the door from above, barring it shut in a way that it is immune to knock (basically, a mini-portcullis falls into holes in the door), while an alarm is set off.

Mix these up, and make sure that the folks in the castle know which lock to use for which door. The alarm might be the simplest solution -- and a good engineer could make one that is both silent and fairly simple (e.g., turning the lock pulls a wire that drops a metal ball into a location-keyed funnel in the guard's chambers, alerting the guard as to which door is being tampered with).

Edit: the other nice thing about this solution is that a burglar might not know what they did wrong: they might think that the door is somehow detecting the knock spell, or that they weren't dextrous enough on picking the lock, or something.

Daniel

 

[Vaxalon]

Two locks per door.

Oh, I LIKE that idea. I like it a lot.

You'd have to deal with wear patterns indicating which lock was the commonly-used one; perhaps a switch on the inside could be used to switch them from one to the other?

Here's an added feature, to deal with any quibbles about whether the dummy lock was 'preventing egress'...

The door has two sets of hinges, one on each side, and sits on a doorsill that is slanted towards the outside. Each lock only undoes one set of hinges. It doesn't matter which one you open, the door swings open on the other set of hinges.

If you use a knock spell, BOTH sets of hinges are undone, and the door falls on top of you! Very good for thousand-pound iron doors with spikes on the front!

Now of course, you still have to deal with people PICKING the lock... they'll probably choose one or the other... but that wasn't the question.

The best thing about this solution is that it's totally mechanical in nature!

 

[Pax]

Oh, I LIKE that idea. I like it a lot.

You'd have to deal with wear patterns indicating which lock was the commonly-used one; perhaps a switch on the inside could be used to switch them from one to the other?

Actually, if the castle-builder has that much money, to do that two-locks-and-an-alarm trick on multiple doors ... make teh locks themselves out of mithril or adamantium, but the keys out of softer iron. Thus, no detectible wear for centuries.

BTW, I like the metal-ball alarm idea. 8) Very nice!

 

[Vaxalon]

Well, actually, you'd have to polish it from time to time, to get the streaks of iron off the lockplate, but I take your point.

Making locks out of adamantium is a good idea for really secure spots, anyways.

 

[Pielorinho]

You'd have to deal with wear patterns indicating which lock was the commonly-used one; perhaps a switch on the inside could be used to switch them from one to the other?

True -- but there are ways around this. Remember that with this security system, you don't need to have particularly good locks: you're relying on trickiness rather than clever tumblers to foil intruders.

As an added level of deviousness, scratch up all the locks a little bit, so that a casual observer can't tell which lock is used and which one isn't. A careful observer might be able to tell the difference. It should be a difficult search check to tell the difference, though.

But then, for your difficult-to-access areas, scratch up the fake lock a little bit more, and make the keys out of hard wood or something similar, so that the careful observer (who thinks she's found a way to foil the system) will open the fake, apparently-more-often-used lock first.

The hinge idea is good, but the problem with it is that it only protects against the knock spell. If the castle's lord (or whoever) has cause to fear lockpicks as well, it won't help -- and I'd guess there are more lockpicks than knock spells running around.

A clever rogue might take 20 on a search check on these locks, and that should foil the trap: the rogue should be able to detect that one of the locks is doing more than just unlocking the door. A wizard, however, won't be able to see that.

Anyway, I'm glad you like the idea!

Daniel