Ronald Knox wrote ten rules on how to avoid ruining a murder mystery with an unsatisfying solution. They apply very well to writing and running RPG modules, with a little alteration.

And just like any module or murder mystery, I’m going to start with a problem, then undress it slowly.

How to Ruin a Story

Suppose your last three sessions have felt like a mini-campaign, bursting with mystery and possibilities.

Now that we’ve captured the baron, how did he get all those goblins into the basement? Did we miss some hidden door to the underdark? Or was the smuggler we got that magic scroll from involved?

        "No, it was magic."

The baron was a mage, this whole time? We didn’t find a single spell-book.

        "Yea, he has a magic wand that does that stuff"

A wand that teleports goblins into basements?

        "Yes.  A wand of goblin summoning"

…wouldn’t they eat him?

        "No, it summons goblins and they do what you say"

…so what did the goblins think was happening when…actually never mind.

This unsatisfying ending could retroactively turn fun evenings into non-fun evenings, and the problems extend far beyond small ‘whodunnit?’ scenarios. Any time a world - even a fantastic world - drops another ‘because magic’, it feels like shit sliding down the story, from its current conclusion, right down to the start. It stops heroes finding interesting solutions. It stops villains plotting how to get away with their crimes. It replaces all thought and planning with the kind of magic that only Harry Potter fans enjoy.

I feel tempted to talk about the importance of keeping things realistic in fantasy worlds, but those ideas will not clarify problems. So instead of realism, let me introduce Knox.

Knox at the Door

Ronald Knox wrote murder mysteries, and wrote advice on writing murder mysteries. In his words:

[The story] must have as its main interest the unravelling of a mystery; a mystery whose elements are clearly presented to the reader at an early stage in the proceedings, and whose nature is such as to arouse curiosity, a curiosity which is gratified at the end.

Most RPGs are not murder-mysteries, but any game which speaks about ’exploration’, or ‘wonder’, or ‘discovery’, or even ‘problem-solving’ pokes at the same basic need to cause curiosity. GMs want to arouse people’s curiosities, and their curiosities must be satisfied.

• Who is this mysterious wizard who claims to be Keraptis?
• What happens when I read this scroll?
• Why are the goblins wearing shoes?

Knox wrote ten commandments for writing murder mystery novels, called ‘a Decalogue’, because if we have a special word which means ‘a collection of ten rules’, then we may as well get some mileage out of it.

The Knox Decalogue

1. The criminal must be mentioned in the early part of the story, but must not be anyone whose thoughts the reader has been allowed to know.
2. All supernatural or preternatural agencies are ruled out as a matter of course.
3. Not more than one secret room or passage is allowable.
4. No hitherto undiscovered poisons may be used, nor any appliance which will need a long scientific explanation at the end.
5. No Chinaman must figure in the story.
6. No accident must ever help the detective, nor must he ever have an unaccountable intuition which proves to be right.
7. The detective himself must not commit the crime.
8. The detective is bound to declare any clues which he may discover.
9. The “sidekick” of the detective, the Watson, must not conceal from the reader any thoughts which pass through his mind: his intelligence must be slightly, but very slightly, below that of the average reader.
10. Twin brothers, and doubles generally, must not appear unless we have been duly prepared for them.

Mutatis Mutandis

The criminal must be mentioned in the early part of the story, but must not be anyone whose thoughts the reader has been allowed to know.

The ‘criminal’, of any story should be involved early on. If the players begin the night focussed on a witch-hunt, and we end the night by revealing a witch in a distant village that they never heard of was casting spells from afar, it can only prompt the response ‘oh, um, okay’; we cannot elicit a satisfied ‘aha!’.

RPG stories do not tend to reveal NPCs’ thoughts, and if they did, it would involve a spell. This culprit-NPC should be innocuous enough that nobody would attempt to read their mind with a spell. ‘The barman who served the troupe their first drink’, or ’the dwarf they bought leather armour from’ both make excellent characters to loop back to, when creating instigators for an adventure.

Of course, many fantasy modules don’t revolve around capturing or killing a single, evil, murderer; the problem can be a magical effect or political squabble. And not every group of PCs will have the ability to read minds or even cast spells. However, it still seems a good rule of thumb that the ultimate cause of any problems should not be presented to the players too directly.

Since the players may suspect any character the GM presents, the GM should attempt to present any culprit through players’ requests, rather than stark introduction. Anything the players ask to purchase is generally beyond suspicion, whether they’re buying weapons from a weaponsmith or hiring a torch bearer.

So the mutated rule should point to introducing broader elements.

The heart of the problem must be mentioned in the early part of the module, but must not be anything the players might attempt to interrogate through spells.

All supernatural or preternatural agencies are ruled out as a matter of course.

This, of course, will need some wide interpretation…from Tolkien.

Supernatural is a dangerous and difficult word in any of its senses, looser or stricter. But to fairies it can hardly be applied, unless super is taken merely as a superlative prefix. For it is man who is, in contrast to fairies, supernatural; whereas they are natural, far more natural than he. Such is their doom.

Magic isn’t supernatural in a magical world. Even if a demonic creature stepped from the shadows, revealing herself to be the one who had given the goblins shoes, this would not need to violate the fabric of a fantasy world; the players could still look behind them, and remember a litany of echoes of demonic power.

However, if the players had never heard of demons before, and the GM revealed that the source of all the problems was a non-corporeal demonic entity, which they could never have suspected before, this would puncture the climax, just as much as ending an old murder-mystery novel by revealing that fairies had done it.

The reveal must not include world-building elements.

Not more than one secret room or passage is allowable.

Steady on, old chap!

…but then again, the fact that rolling for ‘hidden doors’ is a standard task, with standard rules, may not speak well of fantasy RPGs in general.

Personally, I like hidden doors. All I ask of them is that:

1. They have a clear in-world reason to exist.
2. They have a clear description, up to and including how the hinges work (if any).

I never want to see another map that just has a ‘$’ and a key which simply says ‘hidden door’. If anyone can satisfy that the above requirements with ten hidden doors, I don’t see a problem.

No secret room or passage is allowable without a complete description.

No hitherto undiscovered poisons may be used, nor any appliance which will need a long scientific explanation at the end.

Magical items make a perfect analogue here. The are not exactly world-building elements, like in rule number 2, because the players already understand that magical items exist, and have a rough idea of what they might do. However, a new magical item will still make for a poor ending, and this applies to any climax, not only uncovering a mystery.

If a fantastic story poses the question ‘how do we stop all these giants?’, and the answer is simply ‘kill them with that water-freezing wand when they enter the water to bathe’, then can provide a satisfying answer, but only if the wand was introduced earlier in the story. If the penultimate beat of the story is ‘also, you find a wand of water-freezing, so now you can freeze the giants while they take a bath’, then the ending will feel flaccid.

No hitherto unknown magical effect may remain hidden, nor any magical item which has novel magical effects.

No Chinaman must figure in the story.

On first reading, I though Knox didn’t like people pulling out ‘mysterious Oriental people, with mysterious Oriental powers’ as an explanation for a story. But then I looked up his full explanation, and it was just the bog-standard racist stereotypes of the time. So I’m going to take some liberties in updating this for fantasy RPG writing.

Don’t let the story’s motivations rest on lazy stereotypes.

If the players find an ancient religion becoming more popular, and then discover that a vampire has been killing non-believers, then the module can reveal that the vampire instigated the bizarre religious practices in an attempt to bring back the old faith she was raised in. That’s pleasing. It reveals information begging to be leveraged.

On the other hand, if the players find out the vampire kills people to drink their blood, then the players haven’t uncovered something so much as confirmed it.

No accident must ever help the detective, nor must he ever have an unaccountable intuition which proves to be right.

Readers cannot delight in coincidences, because they cannot believe in coincidences. A coincidence means the writer has simply handed out a revelation, which makes it cheap.

Players cannot delight in anything their character discovers with a simple ‘spot check’. However, this rule threatens to go too far. If the players ask to climb a building to get a better view, this may require a roll, and may also reveal a clue. And if the module says that little, yellow shoes have been dropped in the courtyard in a bush, the characters may spot them, even without the players asking to search the courtyard.

If the players ask for a roll, they’re interacting with the mechanics, not the world, and their characters have succeeded, not the player. Similarly, if players ask for a roll to see if an NPC is lying, the GM should not ask for a roll, but instead request what they’re looking for exactly. Are they asking if the farmer seems nervous? Or are they asking if his account makes sense, given everything else they know?

GMs must also not help players by providing solutions. It’s tempting, when players seem stuck, to give them a hint, to tell them to look in this or that place, but the job of the world is to provide questions and curiosity - every attempt to uncover answers should come from the players. So if the players seem stumped, the GM can think of more problems that the world might provide - questions the NPCs might have, additional complaints from farmers, or magical backlash from the chaos-magic which lurks beneath. But never clear answers.

No requests to roll stats must ever help the players, nor must the GM ever provide an unaccountable intuition.

The detective himself must not commit the crime.

Knox clearly wouldn’t approve of evil-aligned parties. In his case, the problem would be an audience who discover the mystery was nothing more than an unreliable narrator. The PCs are in no such danger, but the module is certainly in danger if the PCs create so many problems that their environment must become the solution. If the players spend all their time plotting how their characters commit crimes, then the GM’s job will be looking at how the NPCs respond, and then trying to justify how the NPCs know things, while the GM knows everything.

Modules must focus on PCs solving problems, not causing them.

The detective is bound to declare any clues which he may discover.

Players must know everything their characters know. If the dwarven PC comes from a culture which regularly makes war with goblins, then he should know that goblins don’t normally wear shoes, and so should the player.

The GM is bound to declare any clues which the players’ characters already know.

The “sidekick” of the detective, the Watson, must not conceal from the reader any thoughts which pass through his mind: his intelligence must be slightly, but very slightly, below that of the average reader.

The “sidekick” in an RPG can only mean friendly NPCs, and this advice works excellently for any RPG. Anyone who wants to help the player characters may have excellent information, but they should not have excellent insight. They can prompt the players by asking questions, or answer questions with exactly the kinds of deductions that the players could easily make themselves, but should not elaborate clever plans.

Having NPCs state and restate problems also helps keep all the players on the same page. Every farmer they meet can say again that someone’s stolen their sheep, and that they suspect goblins. Every soldier they meet can suggest tracking the goblins, and stabbing them, but they should not deduce that the goblins must be using their shoes to disguise their tracks.

In the same vein, NPC allies can be strong, but should not propose excellent tactics for fights.

The “sidekick” of the PCs, the henchman, must not conceal from the players any thoughts which pass through his mind: his intelligence must be slightly, but very slightly, below that of the average player.

Twin brothers, and doubles generally, must not appear unless we have been duly prepared for them.

        "It was definitely the baron.  The farmer saw the baron, and had no
        reason to lie.  The butler wouldn't have let anyone into the celler
        except the baron.  It must have been the baron."

It was the baron’s evil twin all along!

        "The only person with enough leather to shoe those goblins was the
        tanner.  The tanner had practiced making shoes for dwarves, who have
        similarly-sized feet.  Only the tanner could have wandered around
        with weapons without arousing suspicion.  It must have been the
        tanner."

But in fact, the shoes were a little illusion-spell. And so was the demon. And the jewels. It was just goblins with illusion spells all along!

Presenting an illusion early in a module will call everything after into question - players will have to double-check everything their characters and any NPCs think they see, carefully. And every check the players think of must let them rule something out - whether they discard a farmer’s account of distant, glimmering treasures, or throw rocks at a demonic apparition to check if it’s just smoke and magic.

But…

Illusion magic, and duplicitous spells generally, must not appear unless the players have been duly prepared for them.

The Module Decalogue

Wrapping it all up, the mutated Decalogue is:

1. The heart of the problem must be mentioned in the early part of the module, but must not be anything the players might attempt to interrogate through spells.
2. The reveal must not include world-building elements.
3. No secret room or passage is allowable without a complete description.
4. No hitherto unknown magical effect may remain hidden, nor any magical item which has novel magical effects.
5. Don’t let the story’s motivations rest on lazy stereotypes.
6. No requests to roll stats must ever help the players, nor must the GM ever provide an unaccountable intuition.
7. Modules must focus on PCs solving problems, not causing them.
8. The GM is bound to declare any clues which the players’ characters already know.
9. The “sidekick” of the PCs, the henchman, must not conceal from the players any thoughts which pass through his mind: his intelligence must be slightly, but very slightly, below that of the average player.
10. Illusion magic, and duplicitous spells generally, must not appear unless the players have been duly prepared for them.