I am writing a OSR-inspired dungeon crawling game, where two key design goals are full GM guidance (in the sense that a beginner GM can follow the rules as written and master a successful game) and zero GM homework (except for the first session, the GM doesn't have to spend any time preparing sessions if they don't want to).

This is the central action resolution mechanic. I'd like it to allow most actions without a die roll, so that the dice are rolled only in a desperate situation where success is unlikely. The same dice rolling procedure is used for combat attacks, and while I want combats to be short and lethal, it's still more rolling than out of combat.

For reference, stats go from 11 to 19.

Player rules

Action resolution: performing Checks

When you attempt a dangerous action or when the GM asks for a Check, take note of the relevant Stat (one of STR, DEX, INT, WIL as determined by the rules or the GM) and roll 2d20.

Every die rolled that’s less or equal to the Stat is a Hit.

If you got:

• At least 2 Hits: success! You achieve your desired result, all is good.
• One hit: failure. You don’t get what you wanted, but there is still hope.
• No hits: disaster! The worst possible outcome.

Difficulty

Some checks, especially against active opponents, have added difficulty.

Difficulty is a number, 1 to 9.

In such checks, you score Hits only if you roll above the difficulty, and also below or equal to your Stat.

If a check would have a Difficulty of 10 or more, the action is impossible and there is no need to roll.

GM rules

Action resolution: how to adjucate players’ actions?

A player just stated they do a thing, and now everyone is looking at you to find out if it works. What do you do?

Find out what they want to accomplish. Make sure you understand both what they want to do, and why they are doing it.

1) If the action is easy or carries no risk, just say yes. Always err on the side of success: the Dungeon and the Wilderness are plenty dangerous enough. 2) Then, ask yourself: what would happen on a Disaster? This is the worst possible realistic outcome. If it hurts the players significantly, or if it is interesting, go ahead, but otherwise - just say yes. Never get yourself stuck arbitrating meaningless rolls. 3) At this point, it’s worth it to make a roll. Choose one of the four Stats based on the attempted actions, and ask for a check.

What Stat?

• STR is for physical activities: forcing a door, jumping across a chasm, hitting somemthing very hard, surviving poison or illness.
• DEX is for finesse: picking a lock, juggling, shooting a bow, weaving a rope, dodging a punch or a thrown stone.
• INT is for memory, analysis and observation: spotting a trap, recalling an obscure detail, understanding a complex mechanism or a magic item.
• WIL is for command, persuasion and resistence to compulsions. Hiring and ordering hirelings, commanding armies, impressing or scaring the opposition, seducing the barman, resisting the call of a succubus.

What difficulty?

When opposing monsters, and sometimes traps or other Dungeon or Wilderness features, the rules provide a difficulty.

When adjucating actions not prescribed by the rules, add two difficulty for each notable hindering factor.

For example, shooting a bow at a target has difficulty zero. Shooting a bow at a target in the dark with notable winds has difficulty four.

Most often, there are no notable hindering factors, and the difficulty is zero.