Faceting an Ability Stone: which line to facet next

Each Ability Stone line holds a fixed number of facets, and every success or failure moves the chance of the next one for the whole stone. Which line you facet next therefore changes how likely you are to reach your target. The Ability Stone Faceting odds calculator takes the results you have so far and gives the exact chance of reaching your target for each line you could facet next.

Record the stone as it stands

Choose your stone on the left, for example the Elegant Stone of Birth, which has 10 facets per line. For each of the three lines, record every facet in order with Record a success and Record a failure, or click a recorded facet to flip its result. Undo last result removes the newest one. Once any facet is done, pick the chance the game currently shows. The calculator refuses a chance that cannot occur after your results.

Set your target

Set how many successes you want on the first and second engraving, and the most successes you accept on the penalty engraving. A new stone starts at 7, 7 and 2, and you can change all three. The target counts the whole stone, so the facets already done count toward it.

A worked case

Every line of the Elegant Stone of Birth has one facet left. The first and second engraving stand at 6 successes and the penalty engraving at 2, the chance shows 75 percent, and the target is 7 and 7 with at most 2 on the penalty line.

• Facet the first or the second engraving next: a 351/1600 chance, which is 21.9375 percent. Either line gives the same chance.
• Facet the penalty engraving next: 39/320, which is 12.1875 percent.

If you facet a positive line first, it has to succeed at 75 percent, the other positive line at the next 65 percent, and the penalty line has to fail at the following 55 percent: 0.75 × 0.65 × 0.45. If you facet the penalty line first, it has to fail at 75 percent, and then both positive lines have to succeed at 75 and 65 percent: 0.25 × 0.75 × 0.65. Facet a positive line first and keep the penalty line for last.

What the calculator does not tell you

When the target can no longer be reached, the page says so instead of showing a chance. How much each engraving gives at each level is unknown, so the calculator compares chances of reaching your target and does not rank the bonuses themselves. The chance steps of 75, 65, 55, 45, 35 and 25 percent are observed values that the game files do not list.