Poison needle traps

Wyvern · May 29, 2018

I recently read a DMs Guild adventure that included a poison needle trap, and I found the wording ambiguous. At first I assumed it was the author's poor choice of wording, but I later found that it was mostly a copy-and-paste from the trap rules in the SRD:

A poisoned needle is hidden within a treasure chest’s lock, or in something else that a creature might open. Opening the chest without the proper key causes the needle to spring out, delivering a dose of poison.

When the trap is triggered, the needle extends 3 inches straight out from the lock. A creature within range takes 1 piercing damage and 11 (2d10) poison damage, and must succeed on a DC 15 Constitution saving throw or be poisoned for 1 hour.

A successful DC 20 Intelligence (Investigation) check allows a character to deduce the trap’s presence from alterations made to the lock to accommodate the needle. A successful DC 15 Dexterity check using thieves’ tools disarms the trap, removing the needle from the lock. Unsuccessfully attempting to pick the lock triggers the trap.

Here's my problem: the final line, "Unsuccessfully attempting to pick the lock triggers the trap," could be taken to mean that *successfully* attempting to pick the lock *doesn't* trigger it. But picking the lock would count as opening it without the proper key, and an unsuccessful attempt to pick the lock wouldn't allow it to be opened in any case. The only way I can think of to reconcile these two statements is that *any* attempt to pick the lock, successful or otherwise, will trigger the trap unless it's already been disarmed. Is that how other people interpret it?

Wyvern

Paul Farquhar · May 29, 2018

It's up to the DM to decide what exactly triggers the trap.

Sometime even using the proper key will trigger the trap unless a secret switch is held down. Check out the suitcase in From Russia with Love.

Imaculata · May 29, 2018

The wording seems pretty clear to me:

"Opening the chest without the proper key causes the needle to spring out"

Lockpicks are not the proper key. So yes, they cause the trap to spring, unless:

"A successful DC 20 Intelligence (Investigation) check allows a character to deduce the trap’s presence from alterations made to the lock to accommodate the needle. A successful DC 15 Dexterity check using thieves’ tools disarms the trap, removing the needle from the lock."

Note that the player must first declare an investigation action to notice the trap. Don't just tell them to make an investigation check, unless they specifically state that they are checking for traps. And failing the disarm-check obviously also springs the trap. Failing to pick the lock in the first place would probably also spring the trap, but that is up to the DM to decide. How sensitive is the trap?

Where these sort of traps usually fail, is that they don't take into account 'how' the player goes about opening the chest, or disarming the trap. If the player just uses a crowbar from the side, that needle is not going to do a thing, even if this does trigger the trap. Likewise, if the player decides to keep his hands away from the lock while trying to disarm the trap, and fails, then the needle shouldn't hit him.

Frankly I would design the trap in such a way that it either shoots a needle in 8 directions outward from the chest, or that it shoots a needle from inside the chest, upward at whoever opens it. Heck, maybe its not even a needle, but a cloud of gas that hits everyone in close proximity to the chest. Having the needle pop out of the lock is awfully specific, and very prone to miss its target.

Shiroiken · May 29, 2018

Imaculata said:
Note that the player must first declare an investigation action to notice the trap. Don't just tell them to make an investigation check, unless they specifically state that they are checking for traps.

Technically passive Investigation should be used here, if the DM uses passive checks.

Imaculata · May 29, 2018

Shiroiken said:
Technically passive Investigation should be used here, if the DM uses passive checks.

Would you passively notice a carefully hidden trap? I think an argument could be made that you should actively search for it. But I guess that is open to interpretation.

DEFCON 1 · May 29, 2018

Here's the other way to look at it: It says "Opening the chest without the proper key"... the use of the word 'proper' is there not to indicate that this specific key is the only thing you can use to open the lock... but merely to distinguish that key from any other key you might use. You could take the word out and be left with 'Opening the chest without the key', or take it out and rephrase it longer as 'Opening the chest without the key designed to open that specific lock'... but they went with just using 'proper' to indicate the specific key for that specific lock.

So the phrase is there to distinguish one key from all the others, but it is not implying that the key, lock, and chest are somehow magical and that there's some sort of connection between them that makes the key the only thing that can open the lock. Instead, like all locks they can be picked.

If you don't use the proper key meant for the lock, then whatever other regular key you attempt to use will hit a couple incorrect tumblers (or some other internal lock mechanic bit) inside the lock which will trigger the needle trap. If you try and pick the lock and fail, you'll hit a couple incorrect tumblers (or some other internal lock mechanic bit) inside the lock as you are picking it which will trigger the needle trap. If you successfully pick the lock, then it means you never hit any incorrect tumblers (or some other internal lock mechanic bit) and thus unlocked it just as if you had the proper key.

Like the others above have said, the DM can rule it however they want. For me personally... needle lock traps are so basic that I just run them at the most basic level-- you stick anything into the lock that doesn't successfully unlock it... the needle gets sprung.

jasper · May 29, 2018

The trap is triggered on the disarm attempt. If the thief misses the DC, he takes damage and rolls the con save. Generally I play if you miss the thieves tool attempt you take the damage.

Imaculata · May 29, 2018

DEFCON 1 said:
If you successfully pick the lock, then it means you never hit any incorrect tumblers (or some other internal lock mechanic bit) and thus unlocked it just as if you had the proper key.

It doesn't say that. It says that only the proper key will not trigger the trap.
Sure, you can pick the lock. But the description doesn't say that the trap won't trigger.

For that you'd either need to disarm the trap (A successful DC 15 Dexterity check), or use the proper key.

Look at it this way: The trap is designed to trigger if you don't use the key. Meaning that the fact that people might find some other way to open the chest is taken into account in the description. That's what the trap is there for: To hit people trying to open it without the key.

Li Shenron · May 29, 2018

A poisoned needle is hidden within a treasure chest’s lock, or in something else that a creature might open. Opening the chest without the proper key causes the needle to spring out, delivering a dose of poison.

When the trap is triggered, the needle extends 3 inches straight out from the lock. A creature within range takes 1 piercing damage and 11 (2d10) poison damage, and must succeed on a DC 15 Constitution saving throw or be poisoned for 1 hour.

A successful DC 20 Intelligence (Investigation) check allows a character to deduce the trap’s presence from alterations made to the lock to accommodate the needle. A successful DC 15 Dexterity check using thieves’ tools disarms the trap, removing the needle from the lock. Unsuccessfully attempting to pick the lock triggers the trap.

[MENTION=6801286]Imaculata[/MENTION], how can you say the wording is "pretty clear"?

It's not even clear whether the description here is for the trap only excluding the lock or if it is for trap and lock together.

(CASE 1)

If you assume the description is complete for the whole thing, then it sounds like you need only one check with thieves' tools for both disarming the trap and opening the lock, provided you first detect the trap. In this case the last sentence "Unsuccessfully attempting to pick the lock triggers the trap" suggests both checks are merged into one.

If you instead don't detect the traps (your Investigation fails or you didn't ever think about it), you automatically trigger the trap, before you finish your lockpicking. After that, since the trap doesn't reset, you can continue without further danger, but you still need to make the DC15 lockpicking check. In this case the last sentence "Unsuccessfully attempting to pick the lock triggers the trap" is irrelevant because the trap is already sprung.

An alternative interpretation would be to allow the character who is unaware of the trap to just lockpick, and not trigger the trap on a success. But then the benefit of a success at detecting the trap would be reduced to more knowledge before deciding whether to not lockpick at all to avoid the danger.

(CASE 2)

But what if instead the description is for the trap only? After all, the DC15 Dex check here mentions only disarm. So it's also possible to read the whole thing as not including the lock, and in fact there are different locks in the book with different DCs for picking them.

In such case, it takes two separate thieves' tools successful checks, one to disarm the trap and another to pick the lock.

If you detect the trap and decide to continue, you do first the disarm check. What happens on a failure? the description doesn't say if a failure in disarm triggers the trap or merely fails at disarming - not that other traps in the DMG specify what happens in this case, but not this trap! If you succeed, then you do the second check to pick the lock.

If you don't detect the trap, I still say it's more reasonable that picking the lock automatically triggers the trap.

As you can see, there are actually lots of options for the DM. The only fixed fact, is that the trap description is everything but pretty clear

iserith · May 29, 2018

It just looks badly worded to me, perhaps an editing error, so it's up to you how it will ultimately function. It seems like the goal here is to set up a challenge of (1) finding the proper key or (2) disabling the trap then picking the lock. Anyone going straight to picking the lock is going to have a nasty surprise. That's how I'd handle it, anyway. I would also be sure to telegraph the existence of the trap in some way so that it isn't a "gotcha."

@Imaculata: A passive check does not imply that the character is being passive. "Passive" refers to their being no roll, not that the character isn't performing a task. In fact, the rules state that such checks resolve a character performing a task repeatedly. Whether the DM uses a passive Investigation check to resolve this situation depends on what, specifically, the player described the character as doing.