Warlock Utility 6Dark One’s Own Luck
Refusing the result that fate has decreed for you, you invoke stars of chaos and uncertainty and try to rewrite what has been written.
Free Action Personal
Trigger: You make a roll you dislike
Effect: Reroll the attack roll, skill check, ability check, or saving throw, using the higher of the two results.
Published in Player's Handbook, page(s) 134, Class Compendium.