Creating moves using the generic d20 method


(He, Him)
Elsewhere I've discussed "flipping" D&D d20 difficulty classes from targets to modifiers, i.e. Very Easy +5, Easy +0, Moderate –5, Hard –10, Very Hard –15, Nearly Impossible –20. Results are then "indexed" like this:

Results (1d20)
•  10+: You do it with little trouble
•  7–9: You do it, but with complications or trouble
•  6-: The GM narrates the consequences

The above is mechanically similar to a PbtA move, as I've emphasised with the wording. A PbtA move is like this:

The basic Outcomes (2d6)
•  10+: You do it with little trouble
•  7–9: You do it, but with complications or trouble
•  6-: The GM says what happens and you mark XP

This allows the implied generic d20 method of modern D&D (stripped of genre and style commitments) to be used to create moves. I say "implied" because the rules for it are drawn from the D&D core books, except the "flipping" part. One can then use (or not use) other modern D&D subsystems for one's design.

What are some of the mechanical features?
  • The linear scale from 1-20 is less sensitive to incremental modifiers (+1, +2 etc) so that more granular bonuses can exist in the game. For example, were one also using the Ability Modifier + Proficiency Bonus structure the linear scale can tolerate the "bounded accuracy" range of +/–20 although generally one would work within +/–10 or +/–12.
  • I think the method is slightly more suitable for playing styles that want to assume an "objective" game world, because there is more scope for circumstantial modifiers. 2d6 can tolerate up to +/–5, although generally designs work within +/–3 or +/–4.
  • I've chosen thresholds above that make the comparison obvious, but I think on d20 other values will make better sense. The middle outcome (success with complications) has high utility for play so should be distributed across a wider range. A set of thresholds I find easy to remember are 10+ / 5+ / Lower, with increased effect on natural 20 and increased consequences on natural 1.
A note on Armor Classes and Saving Throws. One can flip ACs so that attacking moves can use the same method by deducting 10 and making the AC a –ve e.g. D&D plate imposes –8. One can do something similar for saving throw DCs.
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(He, Him)
Congratulations, you just reinvented Talislanta.
It's helpful to have that reference point. What I want to find are where the "natural" or highest utility thresholds fall. Taking a look now at Talislanta 4th ed, the action table presents this index -

0 or less = Mishap
1-5 = Failure
6-10 = Partial success (reduced effect, rather than effect with a hitch)
11-19 = Full success
20 or more = Critical success

Mine is slightly different, and I think there might be some tweaks I can make from knowing the design choices in Talislanta. I currently have this index -

Natural 1 = Mishap
4 or less = Failure with consequences (costs or losses)
5-9 = Success with complication (a hitch in the plan)
10 or more = Full success
Natural 20 = Critical success

I consciously avoid plain failure as it could imply no change to the game state which I think can have low utility for play. That said, it's likely (speaking without having played Talislanta) that in practice costs are paid for the failure. When it comes to mitigated-successes, I prefer to add a hitch than reduce effect... although I suppose a hitch could well be reduced effect.

In play, one impactful difference is that between looking for results below-0 / above-19 versus looking for natural 1s and 20s. Say I have a net +2 on the check? It's impossible for me to have a mishap, and I make a critical success on three numbers (18-20). 15% of my rolls are exceptional, and they can only be exceptionally good. That can also go the other way. I find at the table players always look for special narration when they see a nat-1 or nat-20, so I favour giving those rolls special impact. I've nothing against the above/below approach though... it just has a different set of virtues.

Another difference might be found in the expected modifiers. It looks like Talislanta uses a difficulty modifier range of normally +10 to –10 (but can be greater,) and it looks like ability modifiers are in the range +10 to –10. Skill modifiers start in the range +0 to +5 and look like they can go up to +40. With the thresholds as I have them I would suggest difficulty modifiers +5 to –20. Ability modifiers +5 to –5. And skill modifiers +0 to +10. In play, Talislanta looks to have potentially much wider gaps in net modifiers for actions being attempted.

There's something to learn from Talislanta, and it's fantastic to see a published game with d20-indexed graded outcomes. I think one of the real misses in 5th ed D&D (and unlikely to be changed) is to continue with a "sliding" index. It puts the system a bit behind contemporary RPG tech.

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