Sunday, April 18, 2010

Stepped Charts

An idea bubbled up in my head to use different kinds of dice on the same chart. Some indie games apparently use a mechanic that steps characters through the types of dice to change probabilities of achieving success in skills. So it seemed appropriate to call these Stepped Charts.

It seems like you might be able to use them for two things, but both have some problems.

Concentration of Effect

If you have a chart of bad magical effects, say, and you order it in degree of badness. By using different dice types you can adjust the badness of your result. So, let's say your chart of bad effects looks like this:
  1. death
  2. crippling
  3. blindness
  4. amnesia
  5. muteness
  6. shrink 6 inches
  7. body odor
  8. hair loss
If you want your super-duper evil altar to make really bad things happen when good players touch it you roll a d4. If you medium-evil altar isn't quite as bad you roll a d6, etc. Because the chart is so small, the effect is minimal, but the chance of rolling death goes down the bigger the die you roll.

If you went from d4 to d30 it would go from 25% to 3.3%. If you were ambitious enough to have a 100 entry bad effects chart then stepping from d4 to d100 would change the chance of death from 25% to 1%, a pretty significant change.

I don't know how useful this is, because it's random, and just because you roll percentile, it doesn't mean your poor players won't roll a one. The concentrated effects are always possible, just less likely.

The other possibility I can think of for using Stepped Charts does deal with a kind of certainty:

Exclusion of Effects

If you roll a d4 on the badness chart you can never roll a 5. So, if we look at the chart from the other perspective we might segregate powerful/desired effects at the high end of the range.

Maybe your evil high priest has a Touch of Evil that he rolls on a table for. If you put the most devastating effects higher, you can limit the priest to smaller die types as he climbs in power. If death is entry 30, he can't even possibly kill someone with his touch until he works his way from d4->d6->d8->d10->d12->d20->d30.

The problem here is that uncertainty is still there; the EHP might have the chance of Death by Touch, but if he has to roll on a chart with 30 entries, it's only a 3.3% chance.

Maybe this would still be useful for mercurial domains like divination, or psionics, or wild magic. A psionicist growing in power would have new doors open up to her, new possibilities, but the powers of the mind would always be unpredictable.

Kind of a bummer it doesn't seem more clearly useful, but I thought of a different way to use charts that might be much more helpful to a DM in designing and playing on the fly. That next post . . .


  1. My group's favourite miniatures game, Battlefleet Gothic, uses a similar idea. Ships in that game can take criticals somethings, which get rolled on a 2d6 table, ranging from disabling weapons at the low end, to bulkhead collapses at the high end. However, some attacks are designed to mess with systems, so they just roll 1d6 on the same table (with a 1 doing nothing).

  2. Interesting, it might even be more useful, although a little more complicated if you used modifiers to the chart rolls as well. For example, if the Evil High Priests uses his Touch of Evil on someone who is already weakened then the EHP might get a +1 or +2 depending on how weak the character is. That way even though you might only be roling a d6 then a result of 7 or 8 is still possible. Of course, modifiers should apply the other way as well giving minuses to the roll if a character has certain defenses. Anyway, just an idea or two...

  3. @Jarrah, that sounds pretty close! You come across these ideas and think someone must have done this before. That's why blog comments can be so cool, we can pool our knowledge/experience. Thanks for the example.

    @Zanazaz: Yep, certainly. And people are probably more familiar with the fact that you can get some control just using modifiers on a normal chart roll, something I'd probably call a Sliding Chart, have the same chart for a dungeon but modify up or down according to location, conditions etc.

    Another way to do it is, like in Jarrah's example, with a dice pool. So, you use the same type of die but add more of them. That slowly moves the probability curve up the range.

    I was hoping different die types might be less complicated and less "fuzzy" than modifiers and multiple, averaged dice, but I think the fuzziness just gets moved to trying to determine how to rank your chart entries.