I have created a logical puzzle for a Planescape Campaign I'm preparing. I don't actually know how or when to use it, but I think it might be handy to have something ready in case I ever need a puzzle.
I haven't really tested it (other than solving it by myself), so any feedback is greatly appreciated.
This is a Modron “Authentication System”, used to control access to some place in Mechanus. For security reasons, no single Modron (except perhaps Primus) holds the entire “password”; however, the players can obtain “parts of the answer” (clues) from various Pentadrones in the region. The Pentadrones together could easily access the place, but none of them could do it alone.
In order to solve the puzzle, the players will need many clues, but not all of them. There are far more clues than necessary, so if the players are having trouble they should just go and find some more Pentadrones to get the answers from them. How to get the clues is completely up to the game master and the kind of game the group is playing – perhaps the challenge is just about beating them in combat, or trick them into revealing it, or another kind of puzzle, or playing chess with Modrons. However, make sure to make the challenge interesting enough to go through more than once, and after a few times just fast-forward through the entire proccess (“you want another clue? Ok, you spend more time/resources and get it”). I'm not sure how hard this puzzle would be, but I did not plan it to be a terribly hard puzzle. At the very least the players can control how much extra information they get (and not in a boring “make a check to get more clues” way). Each Pentadrone should have 1-6 clues, depending on how many times you want the players to go through this loop: there are 21 clues and at least 7 are necessary (I think – if you can solve with less, or get to contradictory results, tell me how!). The puzzle itself is:
“In the 27th cycle of the 862nd rotation of this Gear, a wise Archmage, a cunning Bard and a devout Cleric entered Mechanus. Their beliefs could by defined by coordinates along two axis (the Ethical and Logical axis) in a scale of one to three. In the first axis, let the coordinates be named as Evil, Neutral and Good, and on the second axis let them be Illogical, Neutral and Logical. The possible combinations are thus Illogical Evil, Illogical Neutral, Illogical Good, Neutral Evil, Neutral Neutral, Neutral Good, Logical Evil, Logial Neutral, Logical Good. In order to obtain access to sector 234,104,459,223 you must correctly identify the beliefs of the Archmage, Bard and Cleric. For safety reasons, the system will be locked after one failed attempt.”
So, find the alignment of the three characters. Show the characters a handy chart like this to help them (remember, you don’t want to punish them for not being familiar with puzzles like this, so make it as accessible to everyone as possible):
Archmage (A): || Illogical | Neutral | Logical || Evil | Neutral | Good ||
Bard (B): || Illogical | Neutral | Logical || Evil | Neutral | Good ||
Cleric (C): || Illogical | Neutral | Logical || Evil | Neutral | Good ||
Good: at least ___, at most ___
Evil: at least ___, at most ___
Illogical: at least ___, at most ___
Logical: at least ___, at most ___
Instruct them to cross every option they eliminate and circle the ones they are sure of in the first table, and to fill the second one as they find out information, but let them do as they please (use arrows, take notes, whatever). Try to have more than one copy of the first table, it might help to check for different hypothesis or in case it becomes too hard to read or something.
I’ll give the clues first, so you can try to solve the puzzle for yourself first to see how hard/easy and fun/boring it is for your group.
1) The Bard is not Logical
2) The number of Good people is one less than the number of Logical people
3) If the Bard is Good, the Cleric is also Good
4) The number of Evil people is one more than the number of Good people
5) There are less Evil people than Illogical people
6) There is more than one Illogical person
7) If the Archmage is Illogical, no one is Evil
8) If the Cleric is Illogical, the Archmage is Logical
9) If the Archmage is Logical, he is Logical Evil
10) If the Cleric is Good, the Bard is Evil
11) If the Bard is Evil, he is not Illogical
12) If the Bard is Illogical, the Cleric is also Illogical
13) If the Archmage is Good, he is Neutral Good
14) If the Archmage is Neutral Good, no one is Logical
15) If the Archmage is not Good, the Cleric is not Evil
16) If the Cleric is Illogical Neutral, no one is Good
17) There is exactly 1 Evil person
18) The Cleric is not Evil
19) The Bard is not Good
20) The Archmage is not Neutral
21) The Cleric is Illogical
With clues 1-9 it is possible to figure out the puzzle, all the others are just extra hints that might help (or not). They are all true, and may help the players in case they miss something, but I’m not sure how much. The clues 16-21 are more and more direct in order to help desperate groups, but might not be enough to solve the puzzle, so I recommend you hand the clues in this order rather than at random. So, for example, rather than setting which Pentadrones on a map will have each clue, just assume the first one the players find has the first clue and so on. You may mix the clues to make for a longer or shorter challenge, though. The solution is below.
Final solution: The Archmage is Logical Evil and the other two are Illogical Neutral.
Getting to this conclusion:
From clues 1 to 3, you know that there is at most 2 Logical people (since from the 3, one is certainly not Logical), and thus at most 1 Good person (1 less than 2). This means that the Bard is neither Logical nor Good (if he was good, there would be more than 1 Good, which we know there isn't).
Adding clues 4-5, you know there is 1 or 2 Evil people (0+1 or 1+1) and 2 or 3 Illogical people. Clue 6 is redundant, it also gets to “2 or 3 illogical people”.
Clue 7 means the Archmage is not Illogical (since we know there is at least one Evil person), and so the other 2 must be Illogical since there are at least 2 are.
Going back to clue 5 means there is exactly one Evil person, clue 4 means there is no Good people, and clue 2 means there is exactly one Logical – which must be the Archmage. Clue 8 is also redundant, it gets to the same conclusion (Archmage is Logical).
Clue 9 finishes the puzzle. We know who is Logical and who is Illogical (no Neutral on this axis), we know there is exactly 1 Evil and 0 Good people so knowing who is Evil nails it.