Thoughts on a Skill System

 As is tradition, I've been redesigning the Thief¹. Probably nothing novel, I may or may not post it the end.

But I'm drawn to a 2d6 skill system. Why? Partly because of the pleasing bell curve effect - a novice might succeed, a master will almost always succeed. And that eases itself into allowing some advanced thief abilities, i.e. the notorious 'climbing upside down and horizontally, voice skills such as mimicry and ventriloquism, and other skills of deception'. Yes, I have thoughts in that direction.

But there's another reason. Building on Dyson's d6 and 2d6 Thiefin' for Basic Dungeons & Dragons, the 2d6 range lends itself to adding ability modifiers to the roll. Specifically, for a roll-high 2d6 system:

• A 1-in-6 chance requires a roll of 10 or higher
• 2-in-6 requires 9 or higher
• 3-in-6 requires a 7 or 8 - there's no clean way to get a 50/50 outcome on 2d6
• 4-in-6 requires a 6 or higher
• 5-in-6 requires 5 or higher

Why are those numbers important?

Well, if one uses the B/X ability score modifiers, the maximum modifier applied is ±3. Which means, if trying to roll a 1-in-6 chance, even a particularly inept character (with -2 in the relevant ability) can succeed on a natural 12. And if trying to roll against a 5-in-6 chance, a particularly adept character (with a +3 in the ability) is guaranteed to succeed.

Placing success at a modified roll of 10 or more works pretty well with Dyson's table - converting his target numbers to skill modifiers - and also with Open Doors as a skill modified by Strength. Those who are foolish brave enough to delve in dungeons will tend to have some aptitude in this region - a +2 works out about right.

This means that while ability scores are helpful, skill matters more. Even a particularly inept 1st-level Thief, with a +5 to Climb Sheer Surfaces but a -3 to Strength²has a +2 - i.e. about a 3-in-6 chance - of success. They may be feeble, but they know some tricks. 

Yes, I know that skill systems create all sorts of issues. We'll get there. But B/X has a skill system anyway. It just doesn't tell you about it. If you're going to have a Thief, you need to address those issues. We shall get there.

^1: And the Fighter. And the Magic-User. The place of Clerics is undecided. And I'm leaning towards separating Ancestry and Class.

^2: Yes, climbing is modified by Strength, not Dexterity. Not all high-Strength characters need to look like Conan. Fight me.