If your character fails a specific die roll, you can spend one AP to change the die roll to match the desired/required result. This can be done for saving throws, attack rolls, skill checks, finding a secret door, etc.

Also, an AP can be used to grant a reroll at any time for such things as damage rolls, hit point generation, etc. Furthermore, you can use an AP to alter a described result.

Your character starts with a new stat called Adventure Points (AP). Your character has a number of APs equal to their character level.

Each time you gain a level, you add an amount of APs equal to your new level. For example, a 2nd-level character has AP 3 (1 AP at 1st level and 2 additional APs at 2nd level). The adventurer advances to 3rd level and gains 3 APs. If your character had not used any APs, they would now have a total of AP 6.

APs are not regenerated by rest. When used, they are gone until you gain more by level advancement.