13 February 2016

Classic D&D ability checks

When playing classic D&D, I like having some mechanics that don’t reduce the 3–18 range for ability scores to ±3. I’ve been using “roll score or less on nd6” for ability checks. (The n depends upon the difficulty of the check.) It’s unfortunate that this doesn’t take the character’s level into account.

So, here’s what I’m considering:

Roll a d20 for each character level. Pass if any are less than or equal to the ability score.

Although, unlike nd6, this has no provision to factor in a difficulty.

One possibility is to use different dice. For an easier task, roll d12s instead of d20s. For a harder task, roll d30s instead of d20s.

Another possibility is to have the difficulty modify the character’s level. But what do we do when modified level is less than one?

Maybe require rolling score or less on multiple d20s. e.g. If the effective character level were zero, success requires rolling the ability score or less on two d20s.

Here is an Anydice program showing the odds.

4 comments:

Nathan Jennings said...

What about d20+HD greater than or equal to ability score? Easier gets an additional bonus. Harder gets a penalty. Of course, I like the way ability scores are unaffected by level. Some things you got or you don't got, regardless of experience. Thanks!

Nathan Jennings said...

Reread my comment and saw immediately that it wouldn't work! How about d20 subtract HD less than or equal to ability score? That could work! Thanks for your blog.

Robert Fisher said...

Thanks for the comments, Nathan.

The thing about using level as a modifier is that you can end up with things that are automatically successful. If you have an 18, any check against it will be an auto success by 2nd level!

And sometimes that’s OK. But sometimes I want an alternative where failure is always possible.

Of course, you can say that a 20 always fails, but that has never set well with me. That means that at 5th level, a character with an 18 and a character with a 15 are exactly equivalent. And the character with an 18 has the same chance of failure as when he was 2nd level. (And you can get into the ability to absorb penalties, but that’s never been a persuasive argument for not trying to fix the issue to me.)

I also agree that sometimes you don’t want level to be a factor. The thing I leave unspoken here is that what I really want is an array of different solutions so I can pick the one that I think best fits the situation. Sometimes I might use just roll under score. Sometimes I might use roll under score with level as a modifier. Sometimes I might use roll as many dice as you have levels.

Nathan Jennings said...

All good points. Thanks!