Thrall to Demon

(Elder Evils, page 14, DnD 3.5)

[Vile]

You formally become a supplicant to a demon lord. In return for your obedience, you gain a small measure of that demon lord's power.

Prerequisite

Chaotic evil alignment

Benefit

Once per day, while performing an evil act, you can call upon your demonic patron and gain a +1 luck bonus on any one attack roll, saving throw, ability check, skill check, or level check.