Several substances are known to be habit-forming. A character who partakes in such a habit-forming substance runs the risk of becoming Addicted.
Any such habit-forming substance will list an Addictive property, with a die code. For example, Wakefulness Brew is Addictive 2d10. Whenever a character takes an Addictive substance, they increase their dosage count for that substance by one (to a maximum of thirty), and then roll the Addictive dice. If the total rolled is less than the number of doses taken by the character, they have become Addicted.
Each substance has its own rules for the effects of a character who is Addicted. Typically, these effects are negative, and often can be offset by taking another dose. Of course, that increases the character's dosage count, which makes getting off the substance more difficult.
At the start of every day, if the Addicted character did not partake of the habit-forming substance, they reduce their dosage count by one, and roll the Addictive dice. If the total rolled is less than the number of doses taken by the character, they are no longer Addicted. However, their dosage count remains! Completely detoxing from the Addictive substance will require that they stay clean until their dosage count drops to zero.