Critical Skill Checks an Alternative Rule for D20 (DnD/Pathfinder/Starfinder/+)

In our long running DnD Group of 25+ years, we ran an Epic Dungeon and Dragons 3.0 campaign. During this campaign we came across a solution to a problem that had always vexed us with the various D20 rule systems. The lack of critical success and failure on skill checks. The skill system usually always has one problem, if you have people with high enough skill levels you simply cannot fail a skill check and at low levels there are some checks that are just impossible to achieve even if you roll a natural 20. This is because in most D20 systems the normal rules do not have a critical fail or critical success on skill checks, everything else you roll a d20 for has this which makes it generally unintuitive and odd. Making a blanket rule of automatic Success on a 20 or Fail on a 1, create to many odd scenarios and sometimes overpowering or punitive scenarios.

The solution we found was in the "Dungeons and Dragons 3.0 Epic Level Handbook", page 110, heading of "Variant: Open-Ended Rolls". We only applied the roll to Skills and never found it useful to apply to anything else, even when running 20+ level campaigns. Over two decades later we still use this rule on every D20 system we play.

Allowing critical fail/success on skills check can add failure to anything, success to anything and every once in awhile something hilarious. After using this rule for two decades we found it has never proved punitive to those with high skills or overpowering to those with low skills.

The Rule in a nutshell

Whenever you roll a natural 1 on a skill check roll again and subtract 20 from the result. If you roll another 1, subtract 20 again (for -40) and roll again... keep doing this until you stop rolling 1's.

• Example 1: You have a perception of a 5, You roll a 1 on a perception check then you roll an 11 for a total of -4 (-20+11+5). Congratulations you might notice you have a foot... or not...
• Example 2: You have a stealth of an 11, you roll a 1 on stealth and then you roll another 1 on stealth and now another 1 on stealth (Three 1's in a row) and then you roll a 5 for a total of -44 (-20-20-20+5+11). Congratulations the enemies 3 dungeons away hear you and they all attack... you suck go get new dice.

Whenever you roll a natural 20 on a skill check roll again and add 20 to the result. If you roll another 20, add 20 again (for +40) and roll again... keep doing this until you stop rolling 20's or the other players notice your playing with loaded dice.

• Example 1: You have a perception of a 5, You roll a 20 on a perception check then you roll an 11 for a total of 36 (+20+11+5). Congratulations you notice the super secret door that wasn't really there but your dm felt bad because it was a nice roll and nothing was really in the room.
• Example 2: You have a stealth of an 11, you roll a 20 on stealth and then you roll another 20 on stealth and now another 20 on stealth (Three 20's in a row) and then you roll a 5 for a total of 76 (+20+20+20+5+11). Congratulations your so quiet that you can't hear or see yourself.

Clarifications

You do not keep rolling when you roll opposite of the original number, just add your skill to the numbers rolled. This prevents from going from a good roll to a bad roll and limits a wierd chain affect. It's still possible to be positive after rolling a 1 initially, but it would be a low number overall and less likely of success.

• Example 1: You have a Knowledge Check of a 7, You roll a 20 on the check and then you roll a 1, for a total of 28 (+20+1+7)
• Example 2: You have a Jump of a 3, You roll a 1 on the check and then you roll a 20 for a total of a 3 (-20+20+3)

DM Tips

Really sky is the limit, the best bet when something completely weird happens is just make up a good plot point and run with it.

Example:

Someone rolled four 20's in a row and got a 92 Search check, the DM made up on the fly that the person found a dead scout with a map of the area with Points of Interest, including adding a "storage cache". This helped move the story along a little faster and gave some extra help to otherwise lost PC's.

This rule should apply to PC's and NPC's/Monsters equally, It favors the PC's more in the end but it's not remotely overpowering, you can roll equally good or bad (same chance).