A quality die is useful in situations where there is a chance of extraordinary success, but no risk of devastating failure. Read the number as rolled; a 0 counts as 10. If the result is 1, you may roll the die again, doubling whatever number comes up. If a second 1 comes up, reroll and quadruple the next number; a third 1 means multiply the result by 8; and so on.
A stress die is rolled when a character is in a critical situation. People under stress are scared and therefore give it all they’ve got. They are capable of extraordinary feats but can also make disastrous mistakes. Stress rolls can also be called for in situations where there is a chance of great success or abysmal failure, even if the situation is not particularly stressful. If you roll a 1 on a stress die you may roll the die again, doubling whatever number comes up, and so on, just like a quality die roll. If you initially roll a 0 on a stress die, it counts as a 0, not a 10, and you usually must check to see if you botch. To check for a botch, roll again. This second die is called a botch die. If your botch die comes up 0 your character has botched—something has gone horribly wrong. Your character has failed, regardless of the final modified score of the die, and some special penalty, devised by the storyguide, generally applies. In particularly tricky situations, you may have to roll more than one botch die. Each extra 0 rolled increases the severity of your failure. Note that any result other than a 0 on a botch die is disregarded.