A PC wants to jump 10 feet in the air without a running start? No problem. Just look up the difficulty in the Player’s Handbook or Rules Compendium.
A PC wants to “sell” a random traveling merchant the equivalent of the Brooklyn Bridge in your game world for a mere 20,000 gold pieces? Ummm… That’s a difficult DC, right?
Skill DCs can be tough to decide on the fly. Sometimes a difficult DC doesn’t seem to cut it for the crazy thing a PC wants to try, and sometimes you’ll notice DC inflation as you constantly make every skill check high difficulty to challenge highly skilled PCs. How does one navigate the harrowing minefield of skill DCs? Never fear; I will tell you!
Easy DCs: I often look at these as the consolation prize for what would otherwise be a failed check. Example: you ask me what you know about Minotaurs. I have you roll a knowledge check. You roll poorly but still make an easy DC. I tell you common knowledge about minotaurs; they are horned humanoid bull-like creatures that can sometimes be found roaming mazes. So basically, your character gets to know what an average player might know (or a little less) and you save yourself from complete embarrassment.
Other than that, I save easy DCs for rolls that should only be interesting if you roll really low on them. Things like tricking a child (hilarious if you fail) or securing a meeting with the head of the thieves guild (raise suspicion or get into a fight on a failure). Heroes shouldn’t routinely find these things difficult so higher DCs aren’t appropriate, but it can make a memorable session if you roll a 1 or 2 on one of these rolls and get yourself into more trouble.
I should note that I do not use easy DCs for group skill checks, even though this is recommended by the rules. Requiring only half of PCs to succeed on these checks for overall success makes these challenges easy enough; they don’t need to be easy DCs on top of that. I determine the DCs for group checks like any other DC, but I do keep the rule for requiring only half the PCs to succeed.
Moderate DCs: I try to use these as the benchmark for many challenges, despite the fact that highly skilled PCs will virtually always (or literally always!) succeed on moderate checks! I just have to tell myself that they get that perk for investing in those skills and for not trying to do something too crazy. If you are amazing at diplomacy and you want to convince the bandits to parlay with you before they kill you and take your money, then yes, I guess I’m giving you a pass on that one. It’s not an unreasonable thing to do. Convincing them not to attack you without getting any coin for their troubles, on the other hand, would be a difficult check or possibly a skill challenge.
The key to deciding on a moderate DC is to ask yourself “Is there a compelling reason this should be particularly easy or difficult?” If the only answer is “I want rolling skill checks to be exciting” then I think you’ve got to shrug and let this one go. The PCs will enjoy the thrill of totally owning a skill check from time to time enough to make up for the loss of spontaneity. And for those PCs without a stellar skill bonus, this will still be a challenging check!
Difficult DCs: I save these for things where I think “Wow, that would be tough to pull off”, but the task doesn’t border on the realm of ridiculous. So some bandits corner you, and they are looking for some coin; you are part of a group of burly adventurers and explain that you’ll likely mop the floor with them (Intimidate) or offer them a small pittance not to attack you (Diplomacy). You make a difficult check and they go on their way. They don’t have that much riding on the fight so it’s not ridiculous that they would act this way, but they are looking to take all your money, so getting them to settle for less or nothing is not a moderate DC.
Again, even at this level, some PCs will have skills bonuses so high they can routinely pass these checks, almost never failing. Usually this means they invested at least somewhat in that skill, however, so I think you just need to give them a pass. However, I should note I don’t see this as the ceiling for difficulty. Convincing the bandits to JOIN YOU instead of attacking would not be a difficult DC. It would either be more difficult or impossible (I would usually allow the PC to make a roll).
Around this level is where you sometimes want to think about whether a skill challenge would be more appropriate. My rule of thumb: if I want it to be a big encounter, it’s a skill challenge. If I want the story to move on, it’s a skill check.
Difficult + 10: This is a special DC I save for those challenges that are SO difficult that it would be outrageous if the PC succeeded. However, I could still see it being technically possible. Mike Mearles made reference to this type of DC in one of his columns on skill challenges, the idea being this is a kind of super check for highly skilled PCs that would carry extra perks.
Convincing a band of bloodthirsty bandits to join you in your next fight w0uld fall under this category. Tricking a Noble Lord into believing that you are a King from a neighboring country who should be treated with respect and courtesy while dressed in rags might also qualify.
Basically, if it wouldn’t destroy the campaign or all credibility to let the PC get away with something ridiculous, I will let them make a difficult check with a +10 difficulty.
Badass Modifier (-5 DC): I give out the badass modifier for Difficult + 10 checks if, despite being totally ridiculous, I really honestly want the PC to succeed. If the PC proposes something crazy and a burst out laughing at how awesome it is, I will apply the badass modifiers and reduce the difficulty to a mere Difficult + 5.
Summary: Really most of this advice boils down to the following:
- Don’t be afraid to make things hard for your PCs if what they want to do is really crazy and difficult.
- Make things easier if success would benefit the campaign or amuse you.
- Just Say Yes (If Their Skill Bonus is High Enough)