D&D General Is this a fair trap?

[Ruin Explorer]

I've sblocked the trap description:

Spoiler

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.

And here's the source:

Spoiler

Roger Musson, in Best of White Dwarf Articles v 1, p 41 (I don't know which number of the magazine it was first published in; but it's late 70s or maybe 1980).

I voted "No", but for clarity that's because I don't find the trap remotely plausible on a number of levels.

It's one of those deeply meta traps that only exists in the mind of a DM, and couldn't like, sit around for years/decades/centuries. The rope would either rot from age (regardless of anti-Cube chemicals) or be obviously weird, and is positioned in such a way that you couldn't even reach it from the edge of the pit! Dust and so on would build up on the upper surface of the unmoving Cube (which apparently can't climb out? You'd think it could), so it would look weird-as-hell. The block falling on the Cube would not reliably spray it everywhere in the way described, that's a particularly dubious and physics-ignorant idea - it only has what, 10 feet to fall? Even free-falling, in 1g, it's going to get up to less than 10mph. Probably about 6-8mph. So it would be like the cube was hit by a block of stone moving at a jog or very slow run. I'm sure that would penetrate into the cube, and make it bulge outwards, but splatter it wildly? Absolutely not. It's not a swimming pool, for god's sake, which seems to be what he's thinking. It's called a Gelatinous Cube for a reason. At worst people standing immediately next to the pit (most of any splatter would likely hit the ceiling, given the constriction around the pit) might get some on them, but what are they, naked? It's probably going to hit clothes/armour. So you'd want the splatter to roll to hit and the save to be far easier than a normal "oops I walked into it" GC save.

As for Yellow Mold being "subject to a violent fall", that also fails - the block only falls 10' (I am assuming "normal dungeon conditions' - 20' isn't much faster though - it takes 16ft to get up to 10mph even, higher than that is getting into suspicious/ludicrous ceiling heights) and it doesn't hit stone or something, it hit jelly, so will slowly halt. This is not a fall that would injure someone were the jelly in questioning not paralytic and acidic. The wording on what activates a Yellow Mold varies, but this is edge-case as best for activating one.

Further hampering the Yellow Mold is the fire factor. The likely reason the block falls is that the rope and GC are on fire. Possibly from burning oil or magic. Either way the Yellow Mold is on top of a block that is interpentrating a burning Gelantious Cube with a burning rope flopping around, likely going pretty deep into it. So it is extremely likely the Yellow Mold itself catches fire. Which as per 2E at least kills it instantly, no questions asked.

On top of that, if the PCs happen to have Continual Light going, arguably that prevents the Yellow Mold doing anything (it's unclear from 2E if it has to be cast directly on it, but it sure doesn't say that, dunno if 1E is clearer).

So in short:

1) The trap is obviously a trap.

2) The GC should be able to escape and would likely be dusty if it couldn't, and/or full of the skeletons of rats and so on, so easy to see.

3) This relies entirely on the PCs going in absolutely face-first without the slightest hesitation to something that is obviously a trap.

4) The physics of the block-drop just do not work. The block will be moving slowly, and displace rather than splatter the GC, and even if it does splatter it, physics dictates that due to the fact that the GC is in a pit, the splatter will mostly go straight or nearly straight up. It certainly won't hit the entire room, and further, any amount that does go out sideways is likely to be small and may well not hit flesh.

5) The Yellow Mold will not necessarily activate drop a drop as gentle as that, given the deceleration provided by the GC.

6) The most likely scenario to drop the block (fire) also insta-kills Yellow Mold.

That's on top of all the issues with it not being possible to reset, not serving a legit purpose (so couldn't exist unless it was in the dungeon of a wizard who was basically running a deadly version of The Crystal Maze or something), not being able to survive the passage of years and so on.

That's Roger Musson's take on it. He's envisaging that the cube sits a foot or so below the lip of the pit, and that it's not easy to stab/hack down low like that.

If so that means his understanding of physics is even worse than I thought. That would more or less ensure zero horizontal splatter.

 

[R_J_K75]

That's Roger Musson's take on it. He's envisaging that the cube sits a foot or so below the lip of the pit, and that it's not easy to stab/hack down low like that.

Because a foot is such an insurmountable distance to overcome?

 

[clearstream]

That's Roger Musson's take on it. He's envisaging that the cube sits a foot or so below the lip of the pit, and that it's not easy to stab/hack down low like that.

Okay. Let's suppose that it sits enough below the lip that you can't get an angle on it to attack from a safe position. An 11' pit, perhaps.

Seeing as we have specified that the cube doesn't come all the way to the lip, players can bypass the trap by not engaging with it. Presumably the owners keep a plank somewhere nearby.

On the grounds that engaging it is optional, I feel that it is fair.

 

[Ixal]

Because a foot is such an insurmountable distance to overcome?

Every kind of polearm laughs about that distance.
And if the party lacks one of those, lie on your belly, stab with swords.

 

[clearstream]

I voted "No", but for clarity that's because I don't find the trap remotely plausible on a number of levels.

It's one of those deeply meta traps that only exists in the mind of a DM, and couldn't like, sit around for years/decades/centuries. The rope would either rot from age (regardless of anti-Cube chemicals) or be obviously weird, and is positioned in such a way that you couldn't even reach it from the edge of the pit! Dust and so on would build up on the upper surface of the unmoving Cube (which apparently can't climb out? You'd think it could), so it would look weird-as-hell. The block falling on the Cube would not reliably spray it everywhere in the way described, that's a particularly dubious and physics-ignorant idea - it only has what, 10 feet to fall? Even free-falling, in 1g, it's going to get up to less than 10mph. Probably about 6-8mph. So it would be like the cube was hit by a block of stone moving at a jog or very slow run. I'm sure that would penetrate into the cube, and make it bulge outwards, but splatter it wildly? Absolutely not. It's not a swimming pool, for god's sake, which seems to be what he's thinking. It's called a Gelatinous Cube for a reason. At worst people standing immediately next to the pit (most of any splatter would likely hit the ceiling, given the constriction around the pit) might get some on them, but what are they, naked? It's probably going to hit clothes/armour. So you'd want the splatter to roll to hit and the save to be far easier than a normal "oops I walked into it" GC save.

As for Yellow Mold being "subject to a violent fall", that also fails - the block only falls 10' (I am assuming "normal dungeon conditions' - 20' isn't much faster though - it takes 16ft to get up to 10mph even, higher than that is getting into suspicious/ludicrous ceiling heights) and it doesn't hit stone or something, it hit jelly, so will slowly halt. This is not a fall that would injure someone were the jelly in questioning not paralytic and acidic. The wording on what activates a Yellow Mold varies, but this is edge-case as best for activating one.

Further hampering the Yellow Mold is the fire factor. The likely reason the block falls is that the rope and GC are on fire. Possibly from burning oil or magic. Either way the Yellow Mold is on top of a block that is interpentrating a burning Gelantious Cube with a burning rope flopping around, likely going pretty deep into it. So it is extremely likely the Yellow Mold itself catches fire. Which as per 2E at least kills it instantly, no questions asked.

On top of that, if the PCs happen to have Continual Light going, arguably that prevents the Yellow Mold doing anything (it's unclear from 2E if it has to be cast directly on it, but it sure doesn't say that, dunno if 1E is clearer).

So in short:

1) The trap is obviously a trap.

2) The GC should be able to escape and would likely be dusty if it couldn't, and/or full of the skeletons of rats and so on, so easy to see.

3) This relies entirely on the PCs going in absolutely face-first without the slightest hesitation to something that is obviously a trap.

4) The physics of the block-drop just do not work. The block will be moving slowly, and displace rather than splatter the GC, and even if it does splatter it, physics dictates that due to the fact that the GC is in a pit, the splatter will mostly go straight or nearly straight up. It certainly won't hit the entire room, and further, any amount that does go out sideways is likely to be small and may well not hit flesh.

5) The Yellow Mold will not necessarily activate drop a drop as gentle as that, given the deceleration provided by the GC.

6) The most likely scenario to drop the block (fire) also insta-kills Yellow Mold.

That's on top of all the issues with it not being possible to reset, not serving a legit purpose (so couldn't exist unless it was in the dungeon of a wizard who was basically running a deadly version of The Crystal Maze or something), not being able to survive the passage of years and so on.


If so that means his understanding of physics is even worse than I thought. That would more or less ensure zero horizontal splatter.

Isn't this answering - is the trap plausible or good - rather than is it fair?

 

[pemerton]

Every kind of polearm laughs about that distance.

Skilled play!

 

[Crimson Longinus]

Isn't this answering - is the tap plausible or good - rather than is it fair?

It's not fair to subject the poor players to such painfully stupid nonsense.

Players using their wits to figure out how to overcome traps is fun, players trying to deal with demented nonsense that does not follow logic or reason is massively unfun.

 

[Nefermandias]

Traps don't really need to be "fair" tbh. It's more believable if they are designed to kill intruders rather than amuse them.
That said, I would use such tricks only sparingly so the party doesn't become too paranoid.

 

[R_J_K75]

Every kind of polearm laughs about that distance.
And if the party lacks one of those, lie on your belly, stab with swords.

Yup.

 

[clearstream]

It's not fair to subject the poor players to such painfully stupid nonsense.

Players using their wits to figure out how to overcome traps is fun, players trying to deal with demented nonsense that does not follow logic or reason is massively unfun.

Does SP require such suspension of disbelief? Or only definite mechanical terms?

Would it be correct to say that you can't picture something like this trap working? Is that really an SP concern: so long as the DM is consistent and their players are in tune with them?