Disciple of Darkness( Champions of Ruin, p. 23)
You formally supplicate yourself to an archdevil. In return for this obedience, you gain a small measure of the archdevil's power.
Lawful evil alignment,
Hellbound knight (CoR) ,
Once per day, while performing an evil act, you can call upon your diabolic patron to add a +1 luck bonus to any one attack roll, saving throw, ability check, skill check, or level check.