Poison needle traps

Paul Farquhar · May 31, 2018

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

There is no such thing as Passive Investigation. By definition, investigating something is an activity. Passive Perception might notice an external clue if such a clue exists, but otherwise, unless the player says "I am investigating the lock" assume they don't find the trap. A cracksman who tries to pick a lock without investigating it first deserves all they get.

The traps in the DMG and Xanthar's are suggestions. It's up to the DM to decide how the traps in their adventure work.

For example, a trap may be designed to trigger if the "proper key" is rotated clockwise. To open the lock the key must be rotated anticlockwise.

Imaculata · May 31, 2018

Paul Farquhar said:
There is no such thing as Passive Investigation. By definition, investigating something is an activity.

This is what I thought as well. Shouldn't a player declare that they are investigating the lock?

iserith · May 31, 2018

Paul Farquhar said:
There is no such thing as Passive Investigation.

Yes, there is. It follows the definition of passive checks, Basic Rules p. 59. It's also mentioned in the Observant feat. It likely doesn't come up a lot, but it exists.

Paul Farquhar said:
By definition, investigating something is an activity. Passive Perception might notice an external clue if such a clue exists, but otherwise, unless the player says "I am investigating the lock" assume they don't find the trap. A cracksman who tries to pick a lock without investigating it first deserves all they get.

Imaculata said:
This is what I thought as well. Shouldn't a player declare that they are investigating the lock?

Again, from the rules: "A passive check is a special kind of ability check that doesn’t involve any die rolls. Such a check can represent the average result for a task done repeatedly, such as searching for secret doors over and over again, or can be used when the DM wants to secretly determine whether the characters succeed at something without rolling dice, such as noticing a hidden monster."

In order for there to be an ability check - passive or otherwise - there must first be a declaration of action which has (1) an uncertain outcome and (2) a meaningful consequence of failure. The assumption that a passive check means the character is being passive or that the player didn't declare an action is not correct. The character is by definition performing the task repeatedly. Alternatively, the character performs the task once, but the DM wants to keep the result secret. (Though the latter is not my preference.)

Now, whether or not passive Investigation is the "right" passive check to resolve this task is a debatable and what the player described as wanting to do matters. But in order to understand passive checks, you have to understand "passive" refers to there being no die rolls, not that the character is being passive.

Imaculata · May 31, 2018

iserith said:
But in order to understand passive checks, you have to understand "passive" refers to there being no die rolls, not that the character is being passive.

I don't think anyone (myself included) indicated that they didn't understand this.

Skyscraper · May 31, 2018

Imaculata said:
You don't need mystical detection to notice that the inserted key is not the correct one. With a lockpick you could easily hit drums that you're not supposed to hit, and will trigger the trap. I think that's the whole point of the trap; that it triggers if you insert anything but the correct key into the lock.

How, mechanically, would you achieve that? The lock allows the insertion of a key within. If your picks follow the same path, and trigger the same drums, there is no reason that the trap would trigger because the lock is not mechanically triggered any differently than with the key.

iserith · May 31, 2018

Imaculata said:
I don't think anyone (myself included) indicated that they didn't understand this.

Your comments (and the comments of others) seemed to indicate that the player wasn't describing an action for the character. That the character was somehow "passive."

Imaculata · May 31, 2018

Skyscraper said:
How, mechanically, would you achieve that? The lock allows the insertion of a key within. If your picks follow the same path, and trigger the same drums, there is no reason that the trap would trigger because the lock is not mechanically triggered any differently than with the key.

That's not how lockpicking works. When you pick a lock, you try to push all of the drums in the lock until it opens, without being able to see the drums. You are basically relying on feeling, not on sight. If a lock was specifically designed in a way that there are drums that actually trigger an internal mechanism instead, then lockpicks would totally trigger it by accident (and such locks exist by the way!). Because how would a Rogue know what drums to push?

Mistwell · May 31, 2018

Paul Farquhar said:
There is no such thing as Passive Investigation.

That doesn't match the rule very well, which says, "A passive check is a Special kind of ability check that doesn’t involve any die rolls. Such a check can represent the average result for a task done repeatedly, such as searching for secret doors over and over again, or can be used when the GM wants to secretly determine whether the characters succeed at something without rolling dice, such as noticing a hidden monster."

So if a player says they are checking every square of a checkerboard for traps, or every wall in a huge chamber for a secret door, it's perfectly reasonable to use the passive investigation score to do that to save time.

Edit: Doh, Ninja'ed by [MENTION=97077]iserith[/MENTION] !

Mistwell · May 31, 2018

Skyscraper said:
How, mechanically, would you achieve that? The lock allows the insertion of a key within. If your picks follow the same path, and trigger the same drums, there is no reason that the trap would trigger because the lock is not mechanically triggered any differently than with the key.

My understanding is lock picks do not occupy as much of the space in the lock as a key would, and it's theoretically possible the needles are able to exit the lock with the lockpicks inserted while not being able to get past a key in that same space, which is what disables the trap normally with a key.

Satyrn · May 31, 2018

Imaculata said:
That's not how lockpicking works. When you pick a lock, you try to push all of the drums in the lock until it opens, without being able to see the drums. You are basically relying on feeling, not on sight. If a lock was specifically designed in a way that there are drums that actually trigger an internal mechanism instead, then lockpicks would totally trigger it by accident (and such locks exist by the way!). Because how would a Rogue know what drums to push?

Aye.

Or the proper key might have a protrusion on it, so when it's inserted in the lock it presses against a button that prevents the trap from springing. So, when someone uses a skeleton key or lockpicks to open it, they're not bypassing the trap.

Now, this also goes back to what you said earlier in the thread about how the character going about disarming the trap or opening up the chest should affect the result. If the trap works like I just said, it should be readily disabled by jamming the bypass-button down, perhaps with a drop of Sovereign Glue. This would not result in removing the needle like the trap's original description says, though.

And all this leads me to offer up this advice to @Wyvern: When I'm putting in a trap of any sort, I decide on how it works, using the rules only as inspiration or a baseline, changing the details as needed to fit how I picture it working. Then I adjudicate the results of the player's actions. And they don't get to just say "I attempt to disarm the trap;" they have to tell me something like "I'll press the button and apply a drop of Sovereign Glue to hold it in place," or "I'll yank the needle out with my tiny pliers."

But before that happens, I have a successful Investigation check - if the players actually bother trying to figure out how the trap works - tell them all the info I have invented about the trap so they can make an informed attempt at disarming it.

A trap, to me, should be handled rather like a puzzle. I make them rather easy to notice, to the point where I'm often telling the players it's there without any sort of Perception check, because I'd rather focus the game on how they get around it, aiming for scenes like the opening of Raiders of the Lost Ark, or the bits in the Last Crusade just before Indy reaches the Grail.

Also, the trap in question would have to be far more painful for me to bother using, because I also aim for "we're just gonna leave the chest alone for now" to be a choice the players seriously consider alongside "Just have the barbarian open it and soak up the damage."