You empower yourself by drawing on the taint within.
Prerequisite: Mild corruption.
Benefit: Once per day, you can add a bonus on any single attack roll, saving throw, or check. You must make the decision to add the bonus before you roll the die. The amount that you add varies, based on your corruption. If you have mild corruption, then the bonus is equal to +3. If you have moderate corruption, then the bonus is equal to +6. If you have severe corruption, then the bonus is equal to +9.
Source: Heroes of Horror, page 124. Corrected the Prerequisite to list “mild corruption” rather than “mild taint”, which is less specific, as shown in the Benefit text.