The Alexandrian

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Einstein at Dice - Banksy

The act of turning to the game mechanics is, ultimately, an assessment that there is variability in the potential outcome of an action. At the simplest level, we are saying that there is a chance the intention will succeed and a chance that it will fail.

Before we pick up the dice, however, we should take a moment to consider the potential failure state: Failure should be interesting, meaningful, or both. If it is neither, then you shouldn’t be rolling the dice. The clearest example of this is when the response to failure is to simply try it again:

Player: I try to pick the lock.
GM: You fail. What do you do?
Player: I try to pick the lock again.
GM: You fail. What do you do?
Player: I try to pick the lock again.

This is the gatekeeper of mechanical resolution. If the gate is locked (i.e., failure is neither interesting nor meaningful) then you should go back to the spectrum of GM fiat and remember to default to yes.

(It’s equally true that success should be interesting, meaningful, or both. But this generally takes care of itself because the players are not going to propose actions they are not interested in achieving.)

A common mistake GMs make, however, is to think that expending resources is automatically meaningful. For example, the most basic resource that one can expend is time. So they’ll look at the lockpicking example above and conclude that the failed checks are meaningful because they chew up time. However, this lost time only becomes truly meaningful it has consequences (i.e., wandering monsters, time ticking down towards a deadline, enemies on the other side of the door having more time to prepare, etc.).

The actual process by which an action check is made is obviously dependent on the game system you’re using. I’m not going to attempt a complete survey here, but what this usually boils down to is identifying the skill and setting a difficulty.


Identifying which skill to use is pretty straightforward: Each skill will have a description which defines its parameters. You simply need to figure out which skill’s parameters the proposed action fits, and this is usually obvious.

In some cases, you’ll find that the proposed action can fall into the purview of multiple skills. Generally speaking, you can just let the character use whichever skill is better for them. The exception is if you feel that one of the skills is less related to the task at hand than the other: Systems vary in how they handle this, but allowing the check to be made with the alternative skill at a slight penalty is usually a good one-size-fits-all solution. (Another option is to allow a skill check using the alternative skill to grant a bonus to the primary skill. Or, as in D&D 3rd Edition, allowing the character’s expertise in the secondary skill to simply provide a synergy bonus without any check.)

My personal preference is for systems that don’t have a lot of overlap in their skill descriptions. Some overlap is basically unavoidable, but being able to clearly call for a specific check generally streamlines the action resolution process by eliminating the back-and-forth of figuring out whether or not a particular skill would apply to this particular check. This is also why overlapping skills that are frequently used “in the blind” – like a Spot check to notice ambushers – are a particular pain in the ass: Since the player doesn’t know exactly what the check is being made for, they can’t let the GM know if they have an alternative skill they could be using: The GM calls for a Spot Tusked Animal check to notice the brain-eating walrus, but it turns out that the character actually has Spot Carnivorous Sea Mammals at a higher rating.

(Not an actual game. But it should be.)

Not all games have skills, of course. In most of those cases, however, you’ll generally follow the same basic procedure using attributes instead. (In many systems, skills and attributes are actually the exact same thing using different names: You take a single “this is how good I am at doing things” number and you want more detail, so you split it into a half dozen attributes. But then you still want more detail, so you split each attribute into a half dozen skills. It’s only when you get systems that freely pair skills with multiple attributes that the mechanic actually shifts. But I digress.)


There are basically two ways of assigning difficulty:

  1. Look at a list of difficulties and assign the difficulty by either description or analogy.
  2. Start with a “default” difficulty and adjust it by considering the factors that modify that difficulty.

Some systems lend themselves more readily to one approach or the other. For example, D20 systems lend themselves to assigned difficulties and include difficulty tables that say things like, “A Hard task is DC 20.” or “A Formidable task is DC 25.” Call of Cthulhu, on the other hand, lends itself to adjusted difficulties by setting the default target number to the character’s skill rating so that the GM adjusts difficulty by applying a modifier to the rating.

Regardless of the system, however, you can use either technique. (And, in practice, you are likely to use combinations of both.) For example, when running D&D you could easily start with a default difficulty of DC 15 and then say, “Okay, it’s been raining and the rocks are slick, so let’s bump that up to DC 18.”

TAKE 1 / TAKE 10 / TAKE 20

When considering difficulty, there are three additional metrics I find useful. I’m going to use D&D 3rd Edition terminology for them because that was the system where my thinking on this first crystallized. (Players of 4th or 5th Edition may find this confusing because the designers made a really weird decision regarding the handling of “passive” checks such that the description of the D&D 3rd Edition - Player's Handbookmechanics don’t match the mathematics of the mechanics. You’ll just have to suck it up, because I’m not going to try to jump through the broken hoops of poor mechanical design.)

TAKE 20: When you Take 20 in D&D, the result is calculated as if you had rolled a natural 20 on a d20. In other words, it’s the best possible success that the character is capable of achieving. It’s used in situations like our lockpicking example: The character is free to repeatedly attempt the task until they succeed, which means that we can just check the Take 20 to see if it’s a success or not.

TAKE 10: You can Take 10 in D&D when you’re not under any pressure. It’s the average result possible if you were rolling the dice, but the mechanic basically says “this is the level of success the character can achieve if they’re not under pressure or pushing themselves”.

TAKE 1: This concept is not labeled as such in D&D, but it flows naturally out of the mechanic. If you Take 1 on your roll, then it’s the worst result the character can have. If the difficulty of the task is equal to or less than the character’s Take 1, then the character will automatically succeed on that task.

Basically, these concepts break tasks down into three states: What characters succeed at without evening trying (Take 1). What they always succeed at if they make the effort (Take 10). And what they will eventually succeed at if given enough time (Take 20).

(For example, imagine that there’s something hidden in a room that requires a DC 25 Search check to find. A character with Search +5 will always find the item if they take the time to ransack the room. A character with Search +15 will find the item if they just quickly poke around the room. And a character with Search +25 will notice the item just by walking through the room.)

These concepts are generally useful in D&D (and other systems) for streamlining action resolution. But they can be specifically useful when setting difficulty by considering the type of person who would be attempting such actions and then using them as the analogy.

For example, I constructed these tables for D&D 3rd Edition:


Skill BonusLevel of Training
-1 or worseUntalented
+1Basic Training
+20Grand Master
+25Mythic Mastery


DCTaskTake 10 TrainingTake 20 Training
0Very EasyUntrainedUntrained
30HeroicGrand MasterProfessional
35IncredibleMythic MasteryMaster
40Nearly ImpossibleMythic MasteryGrand Master

TAKE 10 TRAINING: Ask yourself, “How much training would it take for someone to be able to succeed at this task as a matter of routine?” Find that level of training on the table and then add 10 to determine the DC of the check (as summarized on the Generic Difficulty Class table).

Example: Even someone without any training in pottery should be able to make a simple, crude bowl if they’re shown how the equipment works, so making such a bowl should only require a DC 10 check (0 + 10 = 10). On the other hand, it takes some training before someone should be able to perform a backflip, so performing a backflip might take a DC 12 check (2 + 10 = 12).

TAKE 20 TRAINING: When dealing with particularly difficult tasks the question to ask is, “How much training would a person need in order to even have a chance to succeed at this task?” Find that level of training on the table and then add 20 to determine the DC of the check.

Example: An average person can’t just pick up a paperclip and pick an average lock. It takes training. So opening an average lock should be a DC 25 check (5 + 20 = 25).

Even if you’re not performing this mental calculation in the moment, this can still be a good exercise to familiarize yourself with what different difficulty numbers really mean in a new system. (I find these techniques particularly useful if you’re trying to calibrate difficulty ratings for characters outside of the human norm.)

But don’t use the character as their own analogy! Setting difficulty by looking at the stats of the character attempting the action and then calculating what you want the percentage of success to be is a pernicious practice. It can seem like a good idea because you’re gauging what an “appropriate” challenge would be for them, but the end result is to basically negate the entire point of having mechanics in the first place.

Infinity - Modiphius EntertainmentSome systems – like D&D or Numenera – lend themselves easily to this kind of analysis. Other systems, however, will obfuscate it. This is often true of dice pool systems. For example, the 2d20 System we use in the Infinity RPG uses a base dice pool of 2d20 which can be expanded through various mechanics up to a maximum pool of 5d20. The target number you’re trying to roll equal to or less than for a success is determined by the character’s skill rating, and the difficulty of the task is rated in the number of successes you need to roll: No matter how skilled you are, there’s no minimum level of guaranteed success. Nor, because of how the ancillary mechanics are designed, is there really a cap on the maximum success you could theoretically achieve.

You could still crank through a bunch of math and get some decent guidelines for dice pool systems like this, but in general you’re probably better off accepting the nature of the beast and using the adjust-from-default method of setting difficulty.

The 2d20 System largely sidesteps these issues, actually, because it doesn’t rely on the GM setting difficulty levels: At least 95% of the time the GM is basically deciding whether the task is of Average (1) difficulty or Challenging (2) difficulty. (Difficulty ratings of 3, 4, and 5 also exist, but are extremely rare in their application.) This is because the system is far less interested in the simple binary of passing or failing the check, and is instead intensely interested in the margin of success the character is achieving.

Which is exactly what we’re going to be discussing next.

Go to Part 6

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23 Responses to “Art of Rulings – Part 5: Skill and Difficulty”

  1. Jonathan Hunt says:

    I really love your tables of skill difficulty for D&D 3.5 and by extension Pathfinder.

    Without meaning to derail too much, it seems a common problem that skill difficulties increase for higher level characters without any real reason… often without any ill intent by the GM or scenario.

    You mention on this in the article, talking about it being a pernicious practice to always match the difficulty to the skill of the PCs. Have you talked about this more extensively in the past? If not I’d love to hear your thoughts on how to handle it, especially for higher level parties or longer campaigns that span many character levels.

  2. Justin Alexander says:

    That really does feel like the sort of thing I surely must have written about in the past, but apparently not.

    The short version is that:

    (1) Leveling up everything else in the world whenever the PCs level up creates the question of why you’re using character advancement at all. One of the dumbest versions of this was the D&D 4th Edition Gamma World, which had every skill check DC set based on the current skill bonus of the PC. You literally could not get better at doing things, but you would nevertheless tally up numbers on your character sheet as if you had a spreadsheet fetish.

    (2) You cut yourself off from exploring the cool stuff that happens when characters actually get better at things.

    There are two forms that this takes. First, there is the cool thing that happens when what was once amazing becomes trivial. At 1st level you tell the story of fighting guerilla warfare against the small goblin tribe. At 20th level, you tell the story of how Sir Branford stood alone upon the White Bridge and held off a goblin legion while his compatriot Larissa the Wise evacuated the city through a planar rift.

    It can be interesting to desperately climb a tree while a pack of wolves nip at your heels. It can ALSO be interesting to glide across the leaves Crouching Tiger, Hidden Dragon-style.

    Second, there’s the ability to explore fantastical things. If DC 15 doors are just wood and simple locks and then, twenty levels later, DC 50 doors are still just wood and simple locks, that’s boring. It’s far more interesting if that DC 50 Open Lock check is, in fact, unknitting the magical weave of a wall of force en route to a DC 75 check that unknits the living soul from the body to which it is locked.

    Which is not to say that every campaign should necessarily be about demigods or whatever. But if there’s a level of competency and power that you’re not interested in exploring, you’re far better off using something like E(X) and limiting the playing space, rather than just ticking up meaningless numbers.

  3. Luca Beltrami says:

    I always read the d&d 4th edition rules as implicitly assuming that the “standard” challenge faced by the characters would be becoming more and more powerful as they levelled up.

    For example lvl 1 characters would be faced with wooden doors, lvl 10 would be metal doors and lvl 20 would involve magically reinforced doors of doom(tm). This was never spelled out in the rules, but followed from assuming that the dc for doing the same exact thing would stay constant over time.

    13th Age manages to frame the same concept much better with the idea of environment tiers (adventurer, champion, epic). The tier determines the default DC for non combat actions, and the party is assumed to adventure in environments of the tier matching their lvl, unless the GM has reasons to bump it up or down. Most importantly the rules describe what similar challenges at each tier could look like

  4. David says:

    I never liked the take 10 mechanic much, as it seems to presuppose you have failed at the previous step of GM fiat and meaningful failure. Additionally, I find it mathematically unsound. Succeeding on a 10 or a 45% chance of failure does not sound like a routine activity to me! Additionally, it introduces far too large a swing in competency. If you succeed on an 11 but not on a 10, the take 10 mechanic means that the next +1 is worth 50%! Additionally, it presupposes that only activities where you fail on a 10 are worth rolling when not stressed.

  5. gullveig says:

    Nice set of articles. Let me put my two cents… In 5e, you could use a difficulty base of 11 (50% of failure) and a Take 5 to adjudicate as automatic success even in “you can’t repeat” cases. It means that if the player can automatically succeed if she has 75% chance of success or more. Because of bounded accuracy (disregarding magic items, spells, special class features, etc), bonuses don’t go up too much (+11 total from +5 attribute and +6 proficiency) and difficulties can be set based on a commoner without any proficiencies.

    Commoners have +0 bonus overall, so they only automatically succeed on difficulty 5 or lower.

    Level 1 players have +5 bonus (+3 attribute, +2 proficiency) on their best skill check, so they can automatically succeed on difficulty 10 or lower.

    Level 10 players have +5 bonus (+4 attribute, +4 proficiency) on their best skill check, so they can automatically succeed on difficulty 13 or lower. They could have bonuses from other sources which may raise the difficulty to 15 or lower.

    Level 20 players have +11 bonus (+5 attribute, +6 proficiency) on their best skill, so they can automatically succeed on difficulty 16 or lower. They could have bonuses from other sources which may raise the difficulty to 20 or lower.

    As you can see (I hope), this automatic success threshold of Take 5 follows the intentions of the system of players being really good at mundane tasks at the first levels and capable of overcoming epic challenges at the highest levels.

  6. Richard P. says:

    When it comes to skill checks I have a hard time with DC on research checks. Especially in a modern setting. I’m running a modern mystery campaign, or starting to, and I am stumped as to how difficult it should be to get information about a person or place. With the internet and Google (not to mention Facebook and twitter) existing in the game world their is readily accessible hoards of data on nearly anything.

    Is this a scanerio you’ve, or another reader has addressed, I how did you get “I’ll Google it” to work in game?

  7. Dan Dare says:

    I would have thought it was a matter of player agency as to how hard an environment the players want to take on. If a 10th level locksmith wants to tool around opening trivial old padlocks then…well…fine.

    If the situations exist with harder locks they should probably have always been there but the player knew they were not competent to take them on yet, maybe through bitter experience.

  8. Justin Alexander says:

    @David: What I like about the Take mechanics is that it effectively systematizes the question of, “When do we need to roll the dice?” And I find it specifically useful in systems where characters have power levels outside of the human norm because it very effectively calibrates those expectations.

    You can certainly skip the Take 10 consideration and only look at Take 1 or Take 20, but that middle ground of “routine unless you’re in combat / stressed / distracted” is conceptually very useful for me and I’d hate to lose it.

    @Richard P.: What you’re talking about there is a mismatch between the expectation that obtaining something in the game should be challenging and the fact that getting that information is not, in fact, challenging to obtain.

    The solution is to accurately model the game world: If the information is trivial for the character to obtain, then just give it to the player. Looking up Bill Gates’ middle name if you have access to Google should be no more difficult than walking across an empty room.

    What good are research checks, then? Well, there’s still lots of stuff that isn’t trivially available. For example, let’s say that I wanted the blueprints to Bill Gates’ mansion. Typing “blueprints to bill gates’ mansion” into Google doesn’t just pop those up. (If I poke deep enough into those search results, though, I can start piecing together information that would probably let me reconstruct it to some degree of accuracy. How accurate? Ah, now we have a reason to make a Research test.)

    More generally: What players DO with information is generally more interesting than the process of obtaining that information. (Although not always: Breaking into secured files in order to snag the blueprints to a billionaire’s house could be quite interesting.) So there’s no reason to create barriers to obtaining that information unless you have a good reason for doing so.

    (You can carry this idea to extremes and conclude that you should, therefore, never deny the players access to any information that they want. But that’s equally silly.)

  9. David says:

    Sure, the rule of thumb of 10 is pretty good for calibrating what the DC ought to be. I suppose what I dislike is the concept of a player-facing take 10 mechanic that players can invoke. As a DM tool or as a way to calculate DCs it works ok (though I would probably pick a different number such as 5 or 7).

  10. Wyvern says:

    “Succeeding on a 10 or a 45% chance of failure does not sound like a routine activity to me!”

    That’s one way to look at it. Another way to look at it is that unless you actually have a penalty to the ability being tested, you’ll *always* succeed at the task, even if it’s something you have absolutely no training in, provided you’re not under pressure. It’s true that being under pressure *could* result in a sharp drop in success rate (from 100% to 55%), but again, that’s only if you have literally *zero* skill. For anyone with a basic level of competence (i.e. a +5, easily achievable at 1st level), there’s only a 20% chance of failure under pressure, and someone who could legitimately be considered an expert will always succeed.

    “I suppose what I dislike is the concept of a player-facing take 10 mechanic that players can invoke.”

    Well… can’t argue with you there. Personally it doesn’t bother me, but I see your point.

  11. Wyvern says:

    “For example lvl 1 characters would be faced with wooden doors, lvl 10 would be metal doors and lvl 20 would involve magically reinforced doors of doom(tm).”

    This discussion reminds me of a review I wrote years ago for an indie RPG called Mythweaver. To quote myself:

    “The level system also applies to locations, in a manner similar to ‘dungeon levels’ in Basic D&D. However, not only are opponents tougher and traps more deadly at higher levels, but locks are harder to pick, objects harder to break, and even the DT of listening at a door increases!”

    Personally, I’ve never considered character advancement rules to be a vital part of an RPG system (after all, most fictional characters don’t radically increase in competence over the course of a story or even series). That said, I’ll admit it’s fun to level up your character in D&D. But if your character doesn’t *feel* more powerful in play, what’s the point? If my character fought wolves at 1st level, then at 10th level he shouldn’t just be fighting tougher wolves. Give me an opponent that requires different tactics to defeat, so that I’ll feel like my skills as a *player* are being challenged.

    Sure, an iron door is harder to break down than a wooden one, but that’s true regardless of your level. If the GM’s idea of providing high-level characters with a decent challenge is to make all the doors iron, how boring. If busting down an iron door at 5th level is exactly like busting down a wooden door at 1st level, then to use a computer analogy, all you’ve done is reskin your doors. “Those ogres you fought last week were *red* ogres. These are *blue* ogres, they’re twice as tough!” Yawn.

  12. Justin Alexander says:

    @David: I can definitely see the argument that Take 5 would provide a gentler statistical shift.

    As far as the mechanic being player-facing, I think the reason that has never bugged me is largely one of perception:

    First, it can be a way for the player to say, “I’m not really stressing about whatever this task is. They’re going about it in a simple, straight-forward, professional way.” which feels like a legitimate in-character declaration.

    Second, I tend to think of the mechanical burden/expertise as something that’s shared by the table. This is particularly true of PC abilities and capabilities. So I don’t perceive a huge difference between me saying, “If you Take 10 here you’ll succeed.” and the player saying, “If I Take 10 here I’ll succeed.” It’s little different than the player saying, “Actually, I’ve got a cloak of fire resistance, so I’ll only take 15 points of damage.” (or whatever).

    @Wyvern: Advancement mechanics can generally take one of three forms:

    (1) You become more powerful. (D&D)

    (2) You become better at more things. (E(X))

    (3) Endurance — you don’t become better, but you can keep doing those things for longer periods of time. (GUMSHOE)

    Games can also mix-and-match these concepts. (Including the exemplar systems I use above.)

  13. Jonathan Hunt says:

    Thank you for the reply, Justin and Luca.

    Levelling up skills for the sake of levelling up skills, with no actual mechanical benefit sounds absurd. Luca’s point about the “standard challenge” becoming more and more powerful does make sense, but I feel it needs to be explicitly mentioned by the GM.

    If a 15th level rogue is in the floating wizard city of Gebzir, trying to open a magically sealed door that constantly modulates itself against intrusion… that seems like it should be challenging for him.

    The problem lies in when our 15th level rogue walks up to a random house in a poor city, and struggles to unlock the door because it’s just as challenging now as it was at 1st level. That just seems so absurd.

    This almost becomes a topic of campaign design, whereby you need to ensure that either the challenges the PCs face are thematically appropriate for their level, or they have the option of choosing such challenges in a sandbox.

    E(X) is an article of yours I somehow have never read, Justin. It proves rather fascinating, yet I fear my players (who were brought up on MMORPGs rather than P&PRPGs) would see it as ‘nerfing’ their characters and subsequently regard it as less fun.

  14. Richard P. says:

    Justin, thanks for the response. That actually makes a lot of sense. I think I was stuck with a rail road mentality where I had decided how I wanted the players to get the information and from what NPC. I often had several options… But none the less I wanted them to play through my preconceived story.

    Thanks for the great information!

  15. Justin Alexander says:

    Something else to consider with Research checks: The outcome of the check doesn’t necessarily need to be the GM delivering exposition. You can also use the outcome to frame the scene where they gain the information.

    The classic example I used is the Gather Information to find out X piece of information by canvassing the docks, so you cut to the seedy union tavern where the PCs finally pull up a chair next to the guy they’ve been told can fill them in.

    Similarly, if you want to use a particular piece of information to point them at a particular NPC, you can use the Research test to do that.

    If the core information they’re looking for would be simple for them to procure, you can still pull this off by offering them the lure of something better. For example, if they want to know where Bill Gates lives, that’s trivial and they can find that out automatically. But if they succeed on the Research test, you can say: “You also find out that his former driver was fired recently. He sounds disgruntled and there are reports he’s been betting heavily down at the tracks.” They’ve got what they want, but you’ve offered them access to something that isn’t trivial.

  16. Randy Hammill says:

    Great stuff. I agree with setting the difficulty based off of a normal person. The PCs aren’t ‘normal’ and therefore a lot of things that are hard for others are easier for them. I also give skilled NPCs the equivalent of a level or level and expertise in the appropriate area. So a sage would have a significant bonus to their Intelligence (History) or Intelligence (Nature), or Intelligence (Arcana), whatever is appropriate.

    I handle resolution a little differently though.

    The skill level and DC determines whether a character can succeed at a certain task. If you have a +5, then you can do anything with a DC of 25 or less. The skill check (roll the die) determines how well you do, or how long it takes.

    The rules define a Passive Check, and imply an Active Check.

    Passive checks are essentially the Take 10 rule. I consider a passive check to be more like a hunch, or a sense that something is wrong. You feel like somebody is watching you, or there’s something not right about the room.

    For an active check, I use a modification of the Take ’20’ rules. Since given the right circumstances and enough time, they can automatically succeed at any task within your capability (that is, the Take 20 rule). The difference between the die roll and the DC is the amount of time (usually in rounds) it takes you to complete the task, and potentially triggers the consequences of failure.

    You’re trying to pick a lock before the guards come down the hall and turn the corner and see you. You have a +5 and roll a total of a 17. You don’t know the DC, but the DM knows it’s a DC 20 and will take you 3 rounds to succeed. You know you can succeed (the DM told you you’re familiar with this type of lock, that is it’s within your skill), it’s just going to take some time.

    If there are consequences (triggering a trap, falling off a ledge, etc.) I allow at least two checks. The first determines if you are immediately successful, and if not how long it will take to succeed. The second check determines the actual success or failure, but the failure results not only in the usual consequences, but also typically imposes the time penalty.

    For example, you are trying to disarm a trap and fail. You hear a click and know something has gone wrong. You need to make another check. If it fails, you trigger the trap. Success means that you don’t trigger the trap, you can try again (with the same process).

    Another example – you are inching along a narrow ledge trying to escape orc archers. Your first failure indicates you slip. You succeed at catching yourself on the narrow ledge, but it’s going to take you 3 rounds to get to a position where you can continue, all within range of the archers.

    Essentially, the idea is to use potential failure to build suspense. The normal skill check process with its default success/fail paradigm doesn’t feel as satisfying as combat with it’s multi-round back-and-forth are-we-going-to-win suspense.

    Opposed skill checks complicate things a bit. For something like Stealth vs. Perception, rolling each round works fine. But for negotiation, a one-and-done check doesn’t feel right.

    For negotiations, etc. I’ve been using the Conversation Reaction table on pg 245 of the DMG as a starting point. The idea is to use Friendly/Indifferent/Hostile as a continuum, and multiple checks will move you toward or away from your goal. You usually start in the middle of Indifferent (They do as asked as long as no risks or sacrifices are involved).

    For research I just extend the time for failure. Instead of measuring in rounds it could be hours. For downtime research it could be days or even months. Setting the actual DC for research may seem tricky, but if it’s for information I want them to have, it will be within their capabilities. They have found a number of journals, and the time component is long rests, as in they will continue to glean new information for each long rest they spend reading it for that period.

    If it’s a question of something they want to research (such as a new spell), then the DC is 20 + the level of the spell. Time is usually measured in weeks, or months if they are researching during long rests (assuming 2-4 hours of research during a long rest).

  17. Dr. Tectonic says:

    “You could still crank through a bunch of math and get some decent guidelines for dice pool systems like this, but in general you’re probably better off accepting the nature of the beast and using the adjust-from-default method of setting difficulty.”

    I have to disagree. The behavior of dice pools can be sufficiently counter-intuitive that I think it’s *more* important to crank through the math to make sure that nothing weird happens when you adjust the difficulty. Witness the original World of Darkness system, where at difficulty 10, the higher your skill the more likely you were to botch.

    If you can program or use a spreadsheet, the math is generally pretty straightforward. It’s just a matter of enumerating the possibilities and tallying up all the outcomes.

    Ideally, though, the game designers will do this for you, and include tables like the ones you’ve generated here in published products…

  18. Wyvern says:


    You made some really interesting suggestions, but there are a few things that aren’t clear to me.

    – If the difference between the die roll and the DC determines how long it takes to succeed, what happens when you roll over the DC? Is there any difference between just barely meeting the target and beating it by a wide margin?

    – How do you determine when a roll is simply *too* low? If your example character had rolled a 6 instead of a 17, would they still have been able to get the lock open? I presume that the character should at least have a high enough modifier to pass the DC on a natural 20, but how do you as GM know if they don’t? Do you ask the players what their modifier is before every roll?

    – I’m not sure I follow your explanation of how you handle rolls with consequences for failure:

    “For example, you are trying to disarm a trap and fail. You hear a click and know something has gone wrong. You need to make another check. If it fails, you trigger the trap. Success means that you don’t trigger the trap, you can try again (with the same process).”

    Do you mean that *any* failure on the first roll risks setting off the trap, or only a failure by 5 or more as in the standard rules? What about the second roll? If you fail the first roll but pass the second, have you made any progress towards disarming the trap or do you have to start over again with your next roll?

    “Another example – you are inching along a narrow ledge trying to escape orc archers. Your first failure indicates you slip. You succeed at catching yourself on the narrow ledge, but it’s going to take you 3 rounds to get to a position where you can continue, all within range of the archers.”

    What determines the 3-round penalty? You said that the first roll determines “how long it will take to succeed” and the second “imposes the time penalty”. What’s the difference?

  19. Randy Hammill says:

    Wyvern –

    – I don’t have any specific ‘succeed by 5 or 10’ events. There are so many possible situations that I’d just do it on a case by case basis. A lot of times success is just success. Either the lock is open or it’s not.

    – I have a chart I’ve put together with the key stats for my players, so I know what their skill modifiers are. There are still some checks I like to roll in secret so they don’t know if they’ve succeeded or not. Plus I need to know their passive checks.

    -Yes, I meant any failure, but I have to admit I don’t recall seeing the failure by 5 or more in the 5e rules. I’ve been DMing since the late ’70’s so there is sometimes a bit (a lot?) of edition creep…Where is that rule?

    Regardless, that simplifies things immensely because now the roll means the same thing. As long as they don’t fail by more than 5, the attempt is successful but just takes more time. If they fail by more than 5, they fail.

    A character with a +4 attempting a DC 15 check will fail 30% of the time. Against a DC 20 it’s 55%. That sounds pretty reasonable (and much better than the 55% and 80% chance of failure it would normally mean).

    So the modified approach:
    Is if possible for them to succeed?
    If fail by more than 5, it’s a failure;
    Otherwise the difference between the DC and the roll is how much time it will take to succeed.

    Something else that has been bugging me in the 5th edition is that there is no difference between trained and untrained. I would suggest that if you are not proficient in a skill you are attempting, then failure is failure and no amount of time (or retries) will allow you to succeed. In other words, you don’t get the 5-point buffer.

    I still think there should be some things that just can’t be done if you aren’t trained though.

  20. Jonathan Hunt says:

    @ Randy Hammill

    I’m not sure what edition of D&D the failure by 5 rule on disarming traps is in, but it is in Pathfinder too.

    “If the check succeeds, you disable the device. If it fails by 4 or less, you have failed but can try again. If you fail by 5 or more, something goes wrong. If the device is a trap, you spring it. If you’re attempting some sort of sabotage, you think the device is disabled, but it still works normally.”

    I really like this system you have presented, and think with some adjustments would actually be an incredibly satisfying set of rules. I would like to know as well how rolls above the required DC might influence events.

  21. Wyvern says:

    @ Randy: It’s a 3rd edition rule; I didn’t realize that there was no equivalent in 5th. It only applies to certain skills, though, where a bad enough failure can leave you worse off than you started: Balance and Climb (you fall), Swim (you sink), and Disable Device (you set it off). I don’t remember any others.

    As to my first question, I wasn’t asking about thresholds of success; what I wanted to know was whether a roll equal to or greater than the DC always takes the minimum amount of time per the skill used, or is there some variation depending on how well you roll?

    I liked the distinction between trained and untrained skills in 3e also, but I think the skills in 5th are mostly general enough that anyone could attempt them. I’d probably make an exception for thieves’ tools (and maybe other kinds of tools as well, including musical instruments); if you aren’t proficient, you can’t even attempt the check.

  22. Gamosopher says:

    (The final “Go to Part 6” is not linked to the sixth part of the series.)

  23. Justin Alexander says:


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