How the DM is in theory meant to run ability checks:
1.set a DC
2. if the player rolls over it, they succeed, otherwise not
How I think everyone actually does it
1. don't set a DC
2. player rolls
3. about 10 or less is a failure
4. about 19 or more is success
5. 11-18, the DM does the thing that makes the story more interesting

or am I unusual in this?

@sil I usually don't set the DC first either. I prefer to see the roll first, and then make a ruling. Although my DC goes from 8 to 30 depending on how easy/hard it is, and I do try to keep it objective.


So a couple of problems with the “setting difficulty after”…

  1. it makes the actual stat worthless and makes the printed number on the die everything. This is where the “d20 is so swingy” myth cames from, if you banana peel moment on a nat 4 or lower and heavens part on a 17+ and your printed bonus, expertise or w/e is never looked at.

  2. it’s so easy to cheat. I never fudge now but I sometimes say that I used to fudge all the time (not woth current group). But it’s not exactly that I would change die rolls. It’s more that I used to do the “setting difficulty after” thing. It quickly became “stat doesn’t matter” and then it devolved into “roll doesn’t matter, either, I’ll just say what I want regardless of the roll”

  3. It’s slower. I know, I know, “Mercer does it” but “Make a strength check, DC 15” is faster than “Make a strength check.” “12.” “Ok, you fail.” and costs less of your attention. It’s also easier math for them; they have +7 they know that only nat eights or higher succeed. This is is especially if there are gonna be several rolls against the same number, such as DC vs an AC.

  4. There is also tension value in them knowing exactly what they need to roll, especially when there are high stakes. If you like me, roll over six, if you don’t, I’ll die. Les jeux sont faits. Rien ne va plus.

  5. Arguably setting after is itself alrrady cheating. It breaks “No paper after seeing rock” principle.

So I always say AC or DC as I ask for a roll.

Most of the time the DC is given from the NPC they’re interacting with, from the module/prep, or from a rule in the DMG. Almost always.

But when it’s not, I have a couple of standards.

  • 40 for “stfu or gtfo” asks like “Do I know the quaint and curious bit of forbidden lore that empires have been shattered to bury?”
  • “The one percenter” when something is so easy, but high stakes, there’s only one percent chance (DC 2 with unmodified dice but advantage) that the bad thing will happen (carrying a valuable egg up a ladder —- even non-adventurers can climb ladders, buuut that egg looks mighty precious), or, conversely, it’s almost a hard no but maaaaybe fate will smile on them (DC 19, disad, unmodified dice).

And then my go-tos. How many outcomes do immediately come to mind? Two? (“Pass/fail”, “live/die”…) then DC 15 (on the modified roll ofc, not natural).

More than two? I call this a twelvetwenty and it might be interesting to you, @sil. Eleven or lower, they get the worst outcome. Twenty or higher, they get the best. Twelve, but not twenty? They get their pick among the rest if there is more than one mediocre outcome, or the one mediocre outcome if I can think of only one. I try to state these outcomes outloud before the dice are rolled. Because murky DM authoity is Not Cool while clear stakes are So Awesome.♥


@Sandra @pench4nt interesting stuff! I'm not necessarily saying that treating a "twelvetwenty" as "DM fiat" is a good thing to do, just that I see lots of DMs doing it, me included :) What you've said here is food for thought, though; thank you!

@sil @pench4nt Yeah, I didn’t mean to come across as super judgy, I was out to sea for twenty years before I landed where I am now. And yeah I know it’s common to do the “just give me a number and we’ll see how I feel”; I just think gameplay can get crisper with set DC♥

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