This spell makes your eyes glow (gold or red, as you prefer) and allows you to see what clerical domains can be accessed by creatures within 120 feet of you. The effect is similar to that of a detect domain spell, but know faith does not require concentration and discerns the location and power of creatures with access to domains more quickly.

You know the location and available domains of all creatures within your sight that have access to cleric domains. If, as a standard action, you concentrate on a specific creature within 120 feet of you, you can determine what gods, outsiders, concepts, or pantheons the creature worships. If the creature is itself an outsider, you learn both its creature type and subtype. Any spell, item, or effect that conceals a creature’s alignment also wards it from the know faith spell.

Know faith can be made permanent with a permanency spell, using the rules for making arcane sight permanent.