How do you deal with traps and locks with keys?

I originally posted this question on the rules forum, but apparently there aren't any hard and fast rules, so I was just wondering how others deal with this. Here's the orginal question:

What are the rules for traps when someone has the key?

For example, your players find a key after an encounter and take it with them. Eventually, they find a chest it fits, but (unknown to them) it is trapped and they don't bother checking and just unlock it, eager to get their hands on the anticipated goodies inside.

Does using the key bypass the trap? Or is the trap independant of the key and so still needs to be disabled (so, in the example above, it will still go off)?

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Do you just play it by ear, have a house rule, or use some other system? Does it make a difference if the trap is a magical one?

Thanks!

My theory is that keys bypass traps in all but very special (DM selected) circumstances.

Traps are dangerous for the owner - having a trap that your key bypasses makes the trap a much lower threat to YOU. It also means you can give the key to somebody else, they can open the chest and NEVER KNOW the trap exists. You are still protected from that person when they return the key.

This also makes it interesting when the party finds three keys. Which one do they try first in that chest? Does using the wrong key set off the trap? (Mostly, yes).

But keys do require a bit more planning for. You have to decide who has them, whether there are multiple keys, what they look like, how hard it is to decide which key goes where, etc... I think the verisimilitude makes it worthwhile. I hate dungeons where every door is locked, but NO KEY is ever found.

The lock and the trap are separate deals, so I normally assume that the key does not automatically disable the trap, and that there is some other mechanism to bypass or disable the trap for those who know it's there. To be honest it's an assumption born of the way my players work anyway, but on occasion there is definitely a chuckle to be had by mixing things up a bit.

Fester said:

Do you just play it by ear, have a house rule, or use some other system? Does it make a difference if the trap is a magical one?

Thanks!

Click to expand...

Generally, I play it by ear.

More specifically, it depends on what that chest was used for, and who it's owner was. I only ever use traps where they make sense (ie, non-high traffic areas, restricted access doors, etc.) and usually there's a bypass of some sort.

In your example, if the owner of the key was routinely supposed to get into the locked chest, then yes, using the key would bypass any associated trap. If the chest was "never meant to be opened" and the key holder was its ancient/mystical guardian, then no, the key wouldn't bypass any associated trap.

So, yeah, by ear.

I think in most cases the lock should disable the trap. The owner of the chest/door/whatever has to have some way to bypass the trap, and usually the key is the most convenient thing.

However, I could see that for particularly valuable objects there may be something else that needs to be done to disable the trap, perhaps a secret panel that needs to be held down while the key is turned, or a magic word that needs to be said. There also could be traps that always go off, if the owner of said trapped object is not vulnerable to the type of trap it is.

Basically, play it by ear. Do what you think would be most appropriate based on the trap's owner and what it's protecting.

I'd say, as in the other thread, that it largely depends on the purpose of the trap, and on how sneaky the trapsetter is.
Does he fear that a subordinate might steal the key? Or does he want to stop anyone (except himself) from getting what is there?

I can see traps where you have to know which knot hole to press to avoid getting that poisoned needle in your finger when opening it (with or without key), or perhaps a magic trap designed to blow up in the face of anyone not wearing the captains hat.

What rules? This is purely a DM decision based upon the purpose and the situation.

In most cases the person who has trapped a chest wants an easy way to open and close it without setting off the trap, and a key is the most obvious and straightforward way of doing so.

It might be that a particularly paranoid person puts a trap on the lock so that if you turn the key the wrong way (the natural way) it sets off the trap, but turn it the appropriate way then it opens. Another alternative is that you have to manipulate a hidden switch on the chest before you turn the key.

It might be that the chest is a decoy explosive trap to destroy the key (and the actual chest is hidden behind a lead-lined secret door!)

Just put a little thought into why someone traps an object and whether they would need access to what is inside it.

Cheers

Normally, I would have decided in advance whether the key also bypassed the trap, or whether the trap will need to be separately dealt with.

If the party has a rogue, or some other character with Trapfinding, I will generally require the trap to be separately dealt with, so the PC gets a chance to use his ability.

If the party has no ability to detect and disable the trap, the key will bypass the trap as well.

I know it sounds metagamey, but I believe in tailoring the challenges in an adventure to the party's abilities.

The majority of the time I would allow the correct key to bypass the trap. The times I wouldn't allow such would be dependent on the nature of the trap.

For instance, most spell traps like glyphs and symbols are set off whenever the conditions are filled. Most other chest traps however are tied to the lock. Hence, I'd let the key bypass them.

The trick is to put all kinds of traps on all kinds of things, not just locks. The bottom panel of the chest could be trapped. It could be resting on top of a trapped pedestal (a la Indiana Jones), so moving the chest itself would spring the trap. Or make the chest permanently invisible.

Be creative. Other things than traditional keys could also be found. Let the PCs open the door with that scrap of paper that says "OPEN SESAME". Whistle the refrain of the evil bard's favorite song, speak the evil one's name (letting him know where you are), have a halfling sit on the child king's throne (or be beheaded), etc. etc.