Subtle EnchantmentsSource Ultimate Intrigue pg. 93
Your enchantments influence targets in more subtle ways and are harder to notice.
Prerequisites: Deceitful, Spell Focus (enchantment).
Benefit: When you cast an enchantment spell or use an enchantment spell-like ability to influence a creature’s attitude or actions and the foe negates the spell with a successful Will save, she has a 50% chance not to notice that she just succeeded at a saving throw (she still can attempt to identify your spell or spell-like ability as normal). If the foe fails the saving throw or is otherwise affected by the spell, the Sense Motive DC to notice she is under the effects of an enchantment increases by 5.
Normal: Anyone who successfully saves against a spell notices the mental intrusion automatically.