Eyes in the Back of Your Head( Complete Warrior, p. 98)
Your superior battle sense helps minimize the threat of fl anking attacks.
WIS 13, base attack bonus +1,
Attackers do not gain the usual +2 bonus on their attack rolls when fl anking you. This feat grants no effect whenever you are attacked without benefit of your Dexterity modifier to Armor Class, such as when you are fl at-footed. You may still be sneak attacked when fl anked.
When you are fl anked, the fl anking opponents receive a +2 bonus on their attack rolls against you.