D&D General Is this a fair trap?

[Charlaquin]

Sure. But problem with 'it's magic' is that ultimately anything can be justified by that and it becomes impossible to conclude anything and make informed decisions. Anything can have any property regardless of what it looks like. You can't conclude things, you must just guess.

Unless of course you want the players to be able to make informed decisions (which I do), in which case you make sure to describe the environment in such a way that gives players the information they need to do so.

 

[Reynard]

Unless of course you want the players to be able to make informed decisions (which I do), in which case you make sure to describe the environment in such a way that gives players the information they need to do so.

Right. Just because the thing is weird doesn't mean it isn't operating based on some sort of internal logic.

 

[Charlaquin]

If it is an unbreakable rope then there certainly isn't a danger of the stone falling? Or is it magically durable only for the purposes of holding the stone but not if players try to damage it? I mean maybe it is an intelligent magical rope? Who knows, it's magic!

High tensile strength, but still combustible. Seems perfectly reasonable to me.

 

[Reynard]

High tensile strength, but still combustible. Seems perfectly reasonable to me.

Or, you know, command word?

 

[Charlaquin]

Or, you know, command word?

That works too.

 

[Quickleaf]

A room contains a 10' cube pit in its centre, with a rope stretched taut between a ring in the bottom of the pit, and a narrow hole in the ceiling through which the rope passes.

There is treasure scattered on the bottom of the pit.

The pit is in fact filled with a Gelatinous Cube (which the PCs can't see either because the GM rules it is naturally invisible, and/or because it has an Invisibility spell cast on it).

The rope is covered in chemicals that (i) protect it from being dissolved by the Cube, and (ii) render it highly flammable. This (ii) becomes relevant should the PCs try to burn the Cube once they discover it (which may be a particularly attractive tactic because it is hard to attack the cube when it's down in the pit), because the rope is in fact supporting a large stone block that sits in the ceiling above the pit (by passing through a hole in the middle of the block, over a hook/pulley that hangs from the true ceiling above the block, and then splits or is knotted into four strands which run to each corner of the block, thereby suspending it).

If the rope burns, the block falls and splats the Cube over everyone, paralysing them. And on top of the block is a Yellow Mould which releases its deadly spoors if subject to a violent fall.[/spoiler]

There's a lot going on with this trap, which means (1) there are going to be a lot of foreshadowing clues, and (2) there needs to be equally strong narrative rationale supporting its ongoing existence.

As long as both of those are met – and if you want I can dive deeper and present some ideas about how to achieve both – then yeah, it's a good trap.

I'd probably also tweak the description to specify the sheer massiveness of the rope – a normal hempen rope that PCs carry around is not going to cut it to support a multi-ton stone block. Probably more comparable to one of those thick ropes from gym class. Or else I'd specify its unusual materiality, like made of braided spider silk or something.

 

[Li Shenron]

I believe they can be a legitimate concern for players. One of the DM's job is to provide a believable world. Now by nature, fantasy, as a genre, will introduce unbelievable elements, but they should be used coherently.

Even for the characters who are accustomed to flying dragons and receiving fireballs in the face, some things remain suspiciously improbable. This usually indicates that there is more to it and that the puzzle is incomplete. The DM, of all people, should have a good grasp of what the "big picture" is.

The trap in question is not a significantly more "suspiciously improbable" than the existence of a gelatinous cube. The trap is very coherent with a world in which gelatinous cubes exist.

There's a level of believability which must be kept in order to avoid suspension of disbelief. But take it too far and it becomes a futile exercise on "who's smarter" which is sadly a very common internet activity, but if you do it at the gaming table, it'll likely do more harm than good to the fun of the group.

 

[Stormonu]

Did a little rendition how I think it might work…

 

[Ruin Explorer]

See, this is where we get into the endless debates about GM-adjudicated things. You are correct, up to a point, IMHO. Beyond that... consider, a 10x10x10 block of stone weighs on the order of FIFTY TONS. It is going to the bottom of that pit, and your cube is going to barely present an obstacle, its going to be squirted out of their like nothing (I am going to assume the trap designer was smart enough to insure that the block is somewhat smaller than the pit's dimensions). Honestly, the big problem would be making sure the block falls cleanly into the pit and doesn't get stuck, etc. but that's an 'engineering' problem and could be plausibly solved.

Where are we get 10x10x10 for the dimensions of the falling block? None are specified AFAICT.

As @Crimson Longinus notes, it's obviously not even remotely possible that it's a 10x10x10 block because it's held up by a single rope, which is not going to hold 50 tons. I read that a 1" rope of the type usually found in D&D can probably hold somewhere up to maybe 8000lbs on a very good day. You're proposing it holds up 112,000lbs, which is, what 14x that? So we can figure that, at most, the block is 1/14th of 10x10x10, so 71 cubic feet. So 4.1x4.1x4.1 maybe? Unless that's not how cube roots work. That's a hell of a lot smaller and 14x lighter - what is going to happen is it will displace some of the goo as it rapidly sinks.

You might claim that could cause splatter, but wait, we've established the pit is 11' deep so it can have the 1' lip described. So that means it has 100' cubic feet of potential displacement before anything goes out of the pit. Which is more than 71' cubic feet. Now the 4x4x4 block is hitting at maybe 6-7mph, so there might be SOME splatter, depending on how viscous the Gelatinous Cube is, but frankly, it can absorb a person walking or running into it at 4-6mph without problems, so I'm guessing even for a much heavier thing with more displacement, it's not going to splatter hardcore. And again, the shape of the pit dictates the spray goes UPWARDS, and then probably comes back down almost vertically. Depending on the exact physics some may go over the edge but won't be much.

You haven't addressed the other various failings of the situation, like the fire killing the Yellow Mold, either.

As for implausible, you're confused.

There's implausible as it unlikely to exist/be set up, which can be excused under certain circumstances or as a genre trope. That's fine, and then there's implausible as in "not believable to function as described". If this trap was implausibly high-tech involving hydraulic pistons or w/e, fine, genre trope. But this is just "dude in 1980 didn't understand basic everyday physics".

But let me revise my "implausible" to "impossible". The trap simply could not function as described. It's so extremely bad, too, that many players will immediately start asking questions about it. If you use it to actually kill PCs, as is intended, those are likely to be quite searching questions and deserving of actual answers.

 

[Laurefindel]

The trap in question is not a significantly more "suspiciously improbable" than the existence of a gelatinous cube. The trap is very coherent with a world in which gelatinous cubes exist.

There's a level of believability which must be kept in order to avoid suspension of disbelief. But take it too far and it becomes a futile exercise on "who's smarter" which is sadly a very common internet activity, but if you do it at the gaming table, it'll likely do more harm than good to the fun of the group.

Believablility and relatability, for the characters, is a fine line that the DM must openly assume or feel from their players. For me, the trap errs on the "too much gratuitous gonzo harms the fun" side if the DM leaves it blatantly gratuitous. Take a wider picture of the same puzzle/trap and things already feel much better for me. Perhaps there are famous gelatinous cube wranglers to link with the dungeon's owner. Perhaps the trap is typical for a certain era, or signed by a famous trap maker, thus setting the construction of the trap between such and such date.

Basically, I want the DM to tell me (in so many words) "this is gonzo beyond the usual, there may be clues as to why it is". From there it can take all kinds of different directions. But I've never been a fan of "it's magical D&D dude, don't fuss over it". I think I could enjoy it in an old-school crawl that has no pretensions, but I'd want to sign-in for that knowingly from the start.