Micro Mechanics: DC Success Thresholds and Phased Encounters

DC Success Thresholds (5e/Shadowdark/etc): Many scenarios up the pressure by specifying something like, “The ritual can be ended with three successful DC 15 Intelligence (Arcana) checks made within 5 feet of the obelisk.” What if instead of saying you need three successful checks, we give it something more akin to hit points?

Let’s say the obelisk has a success threshold (ST) of 30. And let’s say that every 5 of an ability check made against it is deduced from that success threshold, to give us a wider (but staggered) range of successes. So if the wizard goes over to the obelisk and gets a results from 5 to 9 on their check, we deduct 5 from the ST of 30, giving us 25. The next round, they get something from 15 to 19, so we deduct 15, and so on, until it reaches zero. This reduces the granularity of ticking off exact numbers while maintaining our goal of a multiple-check objective.

To calculate the ST, you can just figure out if each check should be Easy, Medium, or Hard difficulty (according to your system of choice), then multiply that by how many checks you want it to take.

In 5e, a three Hard check problem would have a success threshold of 45.

You could also let damage be applied to the ST instead of hit points, or let bad results or enemy actions restore points to the ST.

Phased Encounters (any system): It’s a somewhat common recommendation to reroll repeat results on random encounters tables to avoid, “Giant spiders again??” We can squeeze some more utility out of that by building tables that use multiple dice to make bell curves. The results in the center of the curve are more likely to occur earlier, and then after they’re eliminated, we’ll start seeing more of the outliers.

The neat thing about this is, it’s still possible to roll any result at any time. If you have a 3d6 table with a wizard at 3 and a dragon at 18, you’re more likely to see one of them later in the scenario, but you could be surprised and run into them first thing!

Mixing up dice like “1d8 + 1d6” makes for interesting curves with flat middles.

If you want further guidance on how to respond to repeat results, use the next available lower result when you roll an odd number, and the next available higher result when you roll an even number.

For example, on our 3d6 table, if 5-8 have been rolled already and we roll another 6, we go up the table to 9 because 6 is even. If we roll a 7, we go down to 4.

Bloody Summer: It’s been a busy one. There’s been writing to do, but I have a brief pause so I’m trying to get back to the Iron Fist of the Hobgoblin King. We took out kids to motocross camp in New Hampshire, then I went to Lakes of Fire again. We didn’t host any RPG events because I feel like we’ve done that enough. My one personal offering was a pagan dance hour with songs by Heilung, Faun, etc.

GenCon: is next week. I’ll be running around with few set plans from at least Wednesday through Friday, so if you see me, say hi, or better yet, confound me with a fiendish riddle.

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