An entry in Fortnightly Topic Challenge #39: Deep Down in the Dungeon 1. tl;dr at the bottom

You and your wacky group of adventurers barge through a hidden door and end up in what looks to be the start of a corridor. The door slams shut behind you, leaving you in darkness. Despite your group's best efforts, it won't budge! You're stuck. You take a step forward and suddenly torches that were mounted on the walls light up, one after another in a rapid spree until you can see everything! Well, at least everything in this section of the hall. Looking to your right, you see words carved into the walls -- it reads:

Hah! You think you’re so clever
Believing you’re done at last
Well I’m eager to tell you
the worst has yet to pass

Cannot go backwards, cannot escape
Forward you go, press down a plate
Correctly guess, choose the right shape
On you’ll continue to decide your fate

A Corridor with panels and traps of killer gas
No tricking, avoiding or escaping its grasp
Keep in mind those before
And let their remains warn you
Because there’s no second chances here

As you finish reading it aloud, the group collectively outbursts in despair, "NOT AGAIN!".

What you thought might be a treasure room or an escape out of this unrelenting cave system is actually another trap. DARNIT.

Whelp, there's nothing to do but continue onward as it said. You walk down a bit and reach a pile of dead bodies...which really doesn't look promising. Looking to your left you see four square plates embedded in the wall. An Eye, a Pyramid, an Ouroboros and a Drop. 3 are pressed in, but one of them (which has a Pyramid embossed on it) is still protruding.

After some discussion, you have all decided that the 3 plates that are already pressed in must have released the killer gas and not reset. At least something is FINALLY working in your favor. You press the Pyramid plate down and something clicks....but nothing seems to be happening.

You take a hesitant step forward and aren't dead yet...so you all continue on. As you go down the corridor you find random bodies littered around in various states of decay, perhaps they tried to outrun the gas or who knows what, but they are definitely dead.

You come across another pile of bodies, with another 3 plates pressed in and another Pyramid remaining protruded. You press it in, hear another click, and continue on.

This cycle repeats a few times and you're feeling like your luck has finally changed! All these people died so you don't have to! You proceed to press in a Drop, an Eye, a Pyramid, as Ouroboros and a Drop, each with great success.

Everything is going swell...until you reach the 8th panel. Only two are pressed in. Uh oh. 50/50 chance. What are you going to choose? The Ouroboros or the Drop?

If you make it to the next section, you will find that only one will be pressed in, the Pyramid.

And if you make it past that, you'll see the end of the corridor, you'll be almost there! However...there is one more set of plates on the wall and NONE of them are pressed in. It seems you'll have been the only ones who have made it this far...so now what? Which one will you press?

enter image description here

Map is a visualization of the corridor. Bloody marks are where the panels are and the final panel is marked in green at the bottom.

enter image description here

TL;DR: Which plates need to be pressed in to get past the last three sections and why?

Hint 1

Hmm well what exactly is a corridor?

Inspired by The Thirteen Doors of Aj Noc'la by Alconja

  • 2
    $\begingroup$ Ooh! I like this ... And have absolutely no idea. $\endgroup$
    – Stidgeon
    Oct 3, 2018 at 22:19

5 Answers 5


One thing I noticed about this puzzle is that:

Corners are important.

For example:

As noted in Zenth's answer, the shapes of the different symbols, (and the order in which they are placed on the corners of the map,) suggest that the shapes can be assigned numbers based on the number of corners that they have. The values are:

Ouroboros = 0
Drop = 1
Eye = 2
Pyramid = 3

Let's also mark up the map:

enter image description here

There is one other clue:

As noted in Braegh's answer, one verse in the inscription contains the lines "Keep in mind those before and let their remains warn you." The word "remains" suggests the modulus operation.

Putting it all together:

If we count the total number of corners before each panel, the numbers we get are 11, 15, 21, 34, 43, 48, 57, 64, 70, and 77. If we divide these numbers by 4 (since there are 4 symbols), and then convert the remainders into shapes based on the number of corners, we get the following result:

11 mod 4 = 3 --> Pyramid
15 mod 4 = 3 --> Pyramid
21 mod 4 = 1 --> Drop
34 mod 4 = 2 --> Eye
43 mod 4 = 3 --> Pyramid
48 mod 4 = 0 --> Ouroboros
57 mod 4 = 1 --> Drop
64 mod 4 = 0 --> Ouroboros
70 mod 4 = 2 --> Eye
77 mod 4 = 1 --> Drop

This gives correct symbol for the first seven panels, and shows that the last three symbols are Ouroboros, Eye, and Drop!

Great puzzle!

  • $\begingroup$ You didn't even need the hint, if only I had waited a moment before updating. Yes that's correct! Great job! :D $\endgroup$
    – Sensoray
    Oct 5, 2018 at 20:01
  • $\begingroup$ Can you explain the numbering order? $\endgroup$ Oct 5, 2018 at 20:25
  • 1
    $\begingroup$ @AndrewSavinykh The total count matters, but the exact numbering order doesn't. $\endgroup$
    – Tobbs
    Oct 5, 2018 at 20:32
  • $\begingroup$ So how did it happen that three plates were pressed in at each of the first six panels? $\endgroup$ Oct 6, 2018 at 12:05
  • $\begingroup$ @RomanOdaisky in the puzzle, I state: "plates that are already pressed in must have released the killer gas and not reset" So they were pressed in from other parties and people trying to get through, but they failed and died, hence the piles of dead bodies everywhere. $\endgroup$
    – Sensoray
    Oct 8, 2018 at 12:27

I have some ideas about the shapes:

The Shapes and Iconography lead me to believe there is a number correlation to the symbols. Since the icons each have a place where they come to a "point", and they are written in this order on the image from left to right.

Ouroboros = 0
Drop = 1
Eye = 2
Pyramid = 3

This leads to some issues though in discerning the pattern, I'm working on trying to relate it to the map, and only prior information, but not making too much headway.

With regards to the map, I'm wondering if the red marks where the panels are are "accurate". Specifically The first bloodied area could be on a flat or a point of a "triangle" pattern that would fill the room. (I've done numerous space walking patterns that almost fit but usually break down later in the hall.

  • $\begingroup$ Mmm you might be on to something there ;) $\endgroup$
    – Sensoray
    Oct 3, 2018 at 23:36
  • 1
    $\begingroup$ I'm wondering if the first group to ever try would have had a chance, if they were smart enough to know the pattern? or did some number of previous failure be required for a future group to have any chance. $\endgroup$
    – Zenth
    Oct 4, 2018 at 15:46
  • $\begingroup$ That's a great angle to think at this from! Imagine if you were in the first group to enter the hall? $\endgroup$
    – Sensoray
    Oct 4, 2018 at 15:52

The Legend

For the entirety of my answer, please refer to the legend below:

P = Pyramid
E = Eye
O = Ouroboros
D = Drop


This is a great puzzle! I really enjoyed reading the story, and it has sort of an Indiana Jones feel to it! +1 From me!

Some Ideas

@Zenth brought forward a brilliant idea that the plates are in a numerical order based on their positions on the map. This order is:

O = 0, D = 1, E = 2, P = 3

Considering the fact that most human beings use a $1$ based numerical system, I believe it will actually correlate to:

O = 1, D = 2, E = 3, P = 4

@Stigeon also brought forth a good idea to use mathematical operations to discover the remaining plates which would be a really cool solution to this.

  • I ran the sequence through online solvers in both bases:
  • The four basic mathematical operations were fruitless resulting in:
    • $0$ Based: $13$, $-7$, $0$, $ERROR$
    • $1$ Based: $20$, $-12$, $768$, and $0.021 (Rounded)$.
  • The pattern doesn't seem to have anything to do with placement in specific sections.
  • The side each plate is on doesn't seem to have any significance either.
  • The pattern also doesn't represent a palindrome, modified or otherwise.

My Answer(s)

Currently, the plate order is as follows:

P, P, D, E, P, O, D, O/D, O/E/D, O/E/D/P

  • $\begingroup$ I'm sorry! I somehow left one out of the list and I'm sure that will throw off all of your guess work! I think I accidentally deleted a line, which described the next one. Take my sincerest apologies! I just updated and added it to the list instead. The plates chosen so far should be PPDEPOD. $\endgroup$
    – Sensoray
    Oct 3, 2018 at 20:54
  • $\begingroup$ @Sensoray HAHAHA That made it worse for sure! LOL Still great puzzle! $\endgroup$ Oct 3, 2018 at 20:54

Partial Answer

I suspect there might be some hints hidden in the text:

"Keep in mind those before"

I suspect this is referring to the previously pressed PLATES and not the dead adventurers.

"and let their remains warn you"

If we're going along a number sequence track - could "remains" be referring to remainder-after-division aka modulus?

  • 1
    $\begingroup$ You're right on the money with your second suspicion, nice analyzing ;) $\endgroup$
    – Sensoray
    Oct 5, 2018 at 3:10

Let’s assume that

previous adventurers, when confronted with this corridor, would either (a) press one plate down at each panel or (b) attempt to move past the panel without pressing anything, possibly shifting from strategy (a) to (b) at some point which may or may not be survivable. Let’s also assume that reasonable adventurers would not try multiple plates or start to push plates after surviving without touching one. Unspoken assumptions such as there’s nothing apart from the adventurers that’s interacting with the panels also apply.

We observe that

the first 7 panels all have 3 plates pressed in, then it’s 2, 1 and 0.

Under the assumption above, this is inconsistent with the possibility that

there are plates on panels 1 through 6 that cause death, because that would result in subsequent panels having less plates pressed in

and therefore, it would be reasonable to deduce that

the other panels aren’t dangerous either.

Which is all consistent with

there having been three groups of adventurers that would each hit a random plate up to a certain point where they, convinced that plates do nothing and corpses were brought from elsewhere for intimidation, would stop doing so; plus zero or more groups that would disregard the panels at all.

So the strategy is

to do whatever, but be ready for the next corridor being less forgiving. After all, there’s a corpse source nearby.

  • $\begingroup$ Interesting theory, but there's no lateral-thinking tag. So there IS a solution! $\endgroup$
    – Sensoray
    Oct 3, 2018 at 23:37
  • 1
    $\begingroup$ @Sensoray it better explain how the plates turned out as described by the time the protagonists arrived :−) $\endgroup$ Oct 3, 2018 at 23:41

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