The material below is Open Game Content from a 3PP Source
By swearing to never use a weapon other than a longsword, you can achieve things normally limited to the most highly trained swordsmen.
Prerequisite: Proficient in longsword, Weapon Focus (longsword), base attack bonus +4, worshiper of the Goddess of Valor.
Benefit: You may select longsword-related feats as if you were a 4th-level fighter. For example, you may select Weapon Specialization (longsword) as a feat.
Special: If you ever use a melee or ranged weapon other than a longsword in combat, you lose the benefits of this feat until you receive an atonement spell. You may still use spells that act as weapons (such as flame blade and spiritual weapon) without affecting your oath.