Devil's Favor( Fiendish Codex II: Tyrants of the Nine Hells, p. 81)
You have entered into an infernal pact with a dark power. In return for an indelible stain on your soul, and possibly an eternity of torment in Hell, you gain the ability to call upon the powers of Hell to aid your efforts.
Pact with devil,
When you attempt an attack, save, or check of any sort, you can beseech the dark powers to aid you. You gain a +2 bonus on the attack, save, or check. You can use this ability a number of times per day equal to the total number of devil-touched feats you have selected, including this one.