Jeff Rient’s twenty quick questions for your campaign setting is a useful wake-up call to make sure your setting is capable of handling the sorts of things players are likely to do.
I want to make a list of similar questions that I need to be able to answer as I’m preparing to run a system, since I know they repeatedly come up. I think this could also help if you’re designing a system to make sure you’re including rules (or calling out that you explicitly aren’t including rules) for these common situations.
I think for most of these systems, the answer to most of these questions will be “make it up”. Even in those cases, I think it’s useful to turn unknown-unknowns into known-unknowns and be able to look into how other systems or GMs answer these questions.
Town
How Much Gold Is This Item Worth?
Some treasure is “disguised”
Gresta wears a badly corroded bracelet that appears to be iron, but is in fact platinum washed with iron (125 gp). —Arden Vul
Sometimes NPC appraisers exist
Kellen the jeweler and his wife Maidelle cut, craft, and appraise jewelry, gems, and crystals. —Evils of Illmire
Do PCs automatically know the value of treasures? If not, how do you tally XP or track the secret value? Keep in mind that as they get into the mid levels, their hauls could potentially have hundreds of unique items. Do you want to do book-keeping for all of that?
Then, same deal but for pricing magical items. How much can a player expect to be able to sell a Staff of Striking for?
Can I Sell This Item?
A player loots a marble bust of an ancient emporer that you’ve determined is worth 4000g. They want to liquidate it for gold to pay their expenses (henchman wages, magic items, training, etc). How does selling that work? Do they have to go to a big enough town (which towns are big enough)? Is there a special auction? Can they sell magic items? etc
Can I Buy This Item?
A player wants Gauntlets of Ogre Power. Is anyone selling them? What about in the biggest city? Can they be requisitioned? For how much?
A player wants 100 wheels of cheese (for the Rat King). How long does that take to source?
A player wants to outfit his 30 mercenaries all in Plate Mail. How many suits of Plate Mail are available? What about in the Capital?
Can I Craft This Item?
The party wizard wants to scribe a scroll. Can they? How does it work?
Can I Use This Item?
Lots of these systems have class restrictions on equipment or magic items, but don’t tell the players that until they start finding the items; which gives class-selection regret.
How Does Copying Spells Work?
The player finds a scroll or spellbook. Can they copy the spells into their own spellbook? How long does that take? Is there a chance it fails? Is the original destroyed, or can they still use/sell it? How much is a spellbook worth?
Can I Learn More Rumors?
The party hears about a gang of oddly organized goblins in the Shadow Woods. They want to know if anyone else has any information. They’re willing to spend time or money or both; how does that work?
What Can I Do While The Wizard Learns Spells?
The wizard has their nose in their books for two weeks. Is there anything productive the fighter, thief, cleric, etc can be doing with that time? Ditto if you require training periods to level up like in 1e.
Can I Hire A Thief?
How many adventurers are available in a particular town? A city? What level are they? What class are they? Are their stats good? Can we hire them? What about alchemists or mercenaries? How much do I have to pay them?
How Does Poison Work?
Can I buy it? How quickly does it take affect? Can someone easily detect poisoned food or drink? Am I at risk if I try to poison my arrow?
Travel
How Does Overland Travel Work?
How many encounter checks are you making?
Do you care about weather?
How does getting lost work?
How does food/water work?
How do horses/carts work?
Can you hire mercenary protection or guides? If so, how does that work?
How Does Encumbrance Work?
The players want to carry 30 flasks of oil so they have 120 hours of light (or lots of molotovs). Can they? How much treasure can they carry? What about different weapons for different situations?
Adventure
How Far Can I Jump?
The amount of times where there’s some sort of dangerous floor element that can be solved by simply leaping over it is extremely high. Pit traps, pressure plates, magic glyphs, lava pools, high ledges, etc.
What Does This Magic Item Do?
The players find a magic item. How do they figure out what it does? An instinctual answer might be the players should experiment — I think that works fine for some items (simple +N armor/weapons, for example), but …. less fine for more complicated items:
Guardian Caryatid: This valuable object is prized by those travelers concerned with robbery on the road. It takes the form of a 20”-tall columnar statuette (specific details of the carving vary), formed usually out of ivory or bone. When set on a flat surface and given the proper command word, the guardian caryatid will watch over its owner until a second command is spoken. If certain parameters outlined by the owner occur (motion, noise, light), the caryatid grows to 5’ tall and defends its owner as if it were a 5th-level fighter with AC 6, HP 40; and one attack per round (4-9 HP damage per successful hit). A guardian caryatid may only be hit by magic weapons or spells. It is susceptible to fire, taking double damage from it. —Arden Vul
Again keep in mind that by the mid levels, players might be returning from an adventure with a double-digit amount of such items.
How Does Sneaking Around Work?
The party wants to sneak past guardians. How do you game that out?
Here’s some fictional inspiration
How Does Climbing Work?
Thieves often are given an explicit climbing mechanic, but that’s only for “sheer” surfaces. What about non-thieves? What about easier climbs (like the omni-present rope)? What about other thiefy-skills like picking locks or pockets? What happens if such things fail? Can they be retried?
How Does Finding Secret Doors Work?
Does a player know if they fail the check?
Can they search the same area again if they fail?
How much wall/floor can they cover in ten minutes?
Do Magic Items Count As Treasure?
We typically give XP for treasure — magic items sure look like treasure (swords with jeweled hits and whatnot). If a player finds an enchanted emerald (that would be worth 8000g unenchanted), how much XP do they get when they pull it out of the dungeon? What if they never discovered it was magic?
How Do I Get This NPC To Help Me?
How does negotiation work? Are we rolling reaction rolls or charisma checks, etc? How much does what they say matter vs how well they roll vs how charismatic their character is? Player rizz vs character charisma, etc.
What is the Earshot Range Of Various Common Sounds?
Fighting in happening in a room. Can the NPCs in the next room hear it? What about two rooms down? What about kicking down a door? How far away can a guard hear an invisible spellcaster casting a spell? What about the sound of a group of PCs moving at exploration speed? Can you listen to NPC conversations through doors?
How Do Charm Spells Work?
If a wizard is casting Suggestion, does the victim know? What about Charm Person, or Friends, etc. What about ventriloquism or illusions? How far away is a spell audible from — is it further than the spell’s range?
Does My Guy Know Anything About This?
The party finds a holy symbol bearing a knotted tree, which represents a mildly esoteric god. The players haven’t seen it before (since the campaign is new), but their characters might have. 5e has arcana/religion/etc checks - how does it work in your game?
How Quickly Can I Walk?
How far they can move carefully and quietly in a turn?
How far can they move through an area they’ve been before in a turn?
How far can they walk (like, a normal walking pace rather than careful+quiet) in a turn? How does that impact wandering monster encounters?
Can I Harvest This Monster For Useful Parts?
The players just killed a giant spider. Can they eat it? Can they extract its toxins? Can they make spidersilk armor? Can they skin this dragon and make dragonscale armor?
Fictional inspiration
Combat
How Far Can I Move In A Round?
A player wants to do nothing but run to another spot (to pull a lever next turn, to catch up with an archer, etc). How does that work?
Does the movement speed make sense in the context of the length of a round? Running 120ft in a minute is really slow (a 44 minute mile).
Can I Run Past This Guy?
An orc is standing between you and his shaman. How does getting by the orc work?
Can I Attack And Then Move?
Can the archer shoot and then duck behind cover? Can the fighter kill a kobold and then run out of the room?
Fictional Inspiration
How Does Activating A Magic Item Work?
The player has an amulet where saying the command word “Protectio!” makes them immune to normal missile fire. When do they get to activate it? On their initiative? Can they still move or attack? How many similar activated items can they use on a turn?
How Much Space Do Combatants Take Up?
A PC is surrounded by monsters. How many of them can attack in a round? What if the PC is holding a 5ft or 10ft corridor from a hoard of monsters, how many can attack then? (shoutouts to medieval cat)
Can I Help My Unconscious Friend?
My ally is incapacitated (unconscious, dead, paralysed, etc). Can I drag them to safety? How fast can I move in so doing? Does it just use my movement or my action as well? Or if not my action perhaps it just occupies both hands? What if two or more of us are helping?
How Does Retreating Work?
Either before combat starts, or after it goes south. What happens if the retreat “fails”?
How Does Trying To End Combat Without Death Work?
Is there a morale system? Can the players to try to deescalate combat once it’s started? What if they have the upper-hand? How does that interact with the rest of the combat system?
How Does Drinking A Potion Work?
Can I drink a potion and move or attack in the same round? What if it’s in my pack? How quickly does it take effect?
How Does Invisibility Interact With Combat?
Normally melee engagement prevents movement. Do invisible characters also prevent movement? Does leaving engagement with an invisible character trigger a free attack? How does attacking an invisible character work? How does using a ring of invisibility to go invisible again in combat work?
Here’s some fictional inspiration (heh)
How Does Backstabbing Work?
Thieves tend to get a (vaguely defined) backstab ability. How do you track the facing of enemies? How do you know whether the character is “aware of the thief’s presence”? Can they backstab with ranged weapons? Can they backstab with blunt weapons?
How Does Flanking Work?
The characters are fighting a big Ogre in an open room and want to circle around it to gain some sort of advantage. Does that work? How does circling around something work? What benefit does being on opposite “sides” of the Ogre provide? Do you track which direction the Ogre is “facing”?
How Does Cover Work?
If you’re standing behind a flipped-over table, it’s easy. What if you’re (much more commonly) standing at a corner? Do allies or other enemies provide cover?
How Does Shooting Into Melee Work?
Alice and Bob are locked in combat with two Cultists. Derek wants to shoot the cultist; how does that work?
How Does Death and Dying Work?
A cultist just struck Alice (3hp) for 4 damage. What happens?
How Does Level Drain Work?
You just got hit by a Wight. How should your character sheet update, exactly? Is it reversible?
How Are Race Conditions Resolved?
Normally, this is heavily related to the initiative system. Imagine:
Alice is casting Silence on Zylarthen.
Bob is shooting Yvette (who will die).
Carol is running out of the room.
Xavier is shooting Bob (who will die).
Yvette is charging Alice (who will die).
Zylarthen is casting a Fireball on Alice, Bob, and Carol (which will kill them).
What’s the order of operations?
How Do Maneuvers Work?
How do you shove someone off a cliff? Can you disarm them? Knock them prone? Grapple them? Clamber onto them (rats clambering onto adventurers, adventurers clambering onto dragons)?
Fictional inspiration
How Does The Environment Factor In?
Does cone of cold do more damage to people that are wet? Does it freeze the water and make people slip?
Does lightning bolt do more damage to people that are wet?
Is there an advantage to attacking from high ground?
Does fire damage ignite stuff (like clothes)? If so, how does fire spread?
How does running across a different forms of difficult terrain work? Rubble, ice, mud, deep water, etc.
As someone who is creating a "system" from a mash-up of D&D from old editions and OSR inspired products this is a good list to check off from.
I would add off the top of my head:
What classes can use what specific magic items? If you are pulling from various sources and adding new classes, etc., it will be good to know this beforehand.
How do poisons work?
How does energy (level) drain work?
Here's another which comes up all the time yet I rarely see addressed:
My ally is incapacitated (unconscious, dead, paralysed, etc). Can I drag them to safety? How fast can I move in so doing? Does it just use my movement or my action as well? Or if not my action perhaps it just occupies both hands? What if two or more of us are helping?