Pseudodragon! Heroquest Crits

Instead of the system described in the Pendragon rulebook, it works as follows:

 A roll of "1" is a critical hit.

A roll of "20" is a fumble.

 If your chance of success is 20 or higher, a roll of 20 is no longer a fumble, but it is a failure.

 If your chance of success is 22 or higher, you roll a critical hit if your roll less than or equal to your chance of success minus 20.

For example, if your chance of success is 25, you roll a crit on 5 or less. If your chance of success is 32, you roll a critical hit on 12 or less.

 This method is influenced by the great HEROQUEST RPG by Robin Laws.