Veil of Cyric

(City of Splendors: Waterdeep, page 146, DnD 3.5)

[General]

You have reconciled yourself to the unfortunate truth that hard decisions and regrettable actions are necessary in the service of your deity. You intrinsically rationalize any nongood act, believing your actions to be just and pure.

Prerequisite

Any evil alignment, not an outsider, cannot worship an evil god

Benefit

You do not register as evil to detect evil spells, spell-like abilities, or supernatural abilities unless the aura power (see the detect evil spell, Player's Handbook page 218) of the detector exceeds your own. For example, the aura power of a paladin 7/blackguard 1 is moderate, so a good-aligned cleric would need to be 9th level to detect his evil nature. This feat provides no benefi t against attempts to smite evil or spells such as holy smite or holy word. You are evil, you simply do not register as such to most detect evil attempts.