Possibly the last follow-up question raised by the Situations: The Basics post would be: Why not use a straight Dexterity or Intelligence check, or other ability check?
Obviously, one reason is “Because I really like the idea of skipping rolls.” A unified, unchanging roll is simple to use. Letting players simply skip the roll if their characters are trained or have high ability scores is a big reward that they will appreciate.
But the more typical response of a veteran old school GM is to use “Roll Under Ability” as a solution, either 3d6, 1d20, or 1d100 under the score. This can introduce two issues that might be a problem:
- Some players won’t like “roll under” because it’s the opposite of the way attack rolls and saving throws work. Some people get hung up on “higher is better” and just don’t like “roll under”. You might be able to appease them by treating the roll like Blackjack: higher is better, but the roll can’t be above the ability score. I may have more to say about this in the future.
- A straight “roll under” ability check creates extreme differences between characters. Using a d20 roll under ability check, a character with Strength 3 will have a 15% chance of pushing a heavy lid off a sarcophagus, while an average character with Strength 10 will have a 50% chance, making the Strength 3 character very, very weak in comparison. It makes ability scores extremely important.
One solution, used by the Judges Guild, was to use a d% roll under ability. This makes the range much narrower (3% vs. 10%,) but also makes the chances punishingly low, even for characters with max scores.
A different solution, which eventually became a standard in later D&D editions, is to assign modifiers to different score ranges (-1 for Strength 3-8, +1 for Strength 13-18, no modifier for Strength 9-12.) This helps reduce the impact of differences between scores, but this approach (dice + mods > target) leads to its own issues:
- People become overzealous about using just this method. The end result is people asking “Why not get rid of ability scores entirely and just use the mods?” To which I say “Why not just exert some self control?”
- People become overzealous about target numbers. Most GMs seem to start out with three target numbers (DCs) at a minimum: Easy, Average, and Hard. Not only does this mean they are rolling too often (Use Rope or Wear Pants skill rolls,) but the open-ended nature of the roll tempts them into adding more DCs, which makes ability scores or other sources of stacking modifiers more important, which means leads to hacking to extend the ability score range or add buff spells, which leads to GMs saying “Now I need even more DCs to keep my players challenged,” and the death spiral of modifier overkill begins.
Dice + Mods > Target can be OK if it is very restrained, for example the Target 20 system (one target number) plus minimal ability bonuses, and preferably only one other modifier (no stacking mods.) Still, a system that lets players skip rolls most of the time seems far more preferable and avoids all the problems listed above.
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