A Simple Algorithm for Generating DCs

As has become something of a habit for me lately, I wrote an adventure on the plane ride home from GenCon. Lately, it's rare that I have 3 to 4 consecutive hours to do anything other than (sometimes) sleep.

I'm a big believer that laziness is the mother of insight. Many folk see a tendency toward sloth as a bad thing, but if not for sloth, we'd still be living in caves, hunting brontosauruses, and hiding from thunderstorms. It's the human capacity for laziness that drives us to make short term sacrifices (inventing science was no easy feat) for long term pay offs (computers for everyone!).

Thus, I found myself writing an adventure while wedged into seat 24D with a pencil box, a notebook, and two Forgotten Realms sourcebooks (the new 4e one and the DM's book from the old gray box). I had put my D&D books into my luggage because, frankly, I didn't want to carry them around.

The monsters were pretty easy to generate for the adventure - I either remembered their levels, or I built them from scratch (the formulas are easy peasy to memorize, and again my commitment to laziness pays off - I don't need to carry the DMG).

However, I was a little annoyed when working on traps, terrain features, and just general stuff that needed DCs. I couldn't remember the DC progression. I puzzled over it for a few minutes, then realized that my laziness had saved me once again. In an insight so obvious that I feel like punching myself, here's Dr. Mearls' Patented, Super Easy, Instant DC Generator:

1. Start with 10.
2. Add half the trap, encounter, or challenge's level.
3. Do you want only people trained in the skill to have a shot at success? If so, add 5.
4. Think of the stat a PC would need to have a 55% chance of success, assuming the PC is trained if you want only trained guys to have a chance of success. Add that stat's modifier.

Voila! Instant DC.

Here's an example:
In a dungeon aimed at 6th level PCs, there's a locked door. It's a really good lock, so only a rogue or someone trained in Thievery has a chance to open it, but someone who is trained doesn't need much natural talent to open it.

So:
10
+ 3 (half of level 6)
+ 5 (assume training)
+ 1 (a Dex 13 character who is trained should be able to handle this one)

Is a total DC of 19. Voila! An untrained character with a good Dex still has a 30% chance to open the lock.

If you know the PCs' stats, you can achieve a fine control of the DC by using the process above, plugging in the PC's stat mod, then adding 1 to the DC for every 5% you want to drop the success chance.

The nice thing about this method is that it pushes you to think of what the PCs can do, and it's simple enough (IMO) that you can use it on the fly.

OK, back to taking care of all the chores that have piled up since I've been away. I'll talk about GenCon later this week.