Warrior Spirit (Su)Source Magic Tactics Toolbox pg. 10
The fighter can forge a spiritual bond with a weapon that belongs to the associated weapon group, allowing him to unlock the weapon’s potential. Each day, he designates one such weapon and gains a number of points of spiritual energy equal to 1 + his weapon training bonus. While wielding this weapon, he can spend 1 point of spiritual energy to grant the weapon an enhancement bonus equal to his weapon training bonus. Enhancement bonuses gained by this advanced weapon training option stack with those of the weapon, to a maximum of +5.
The fighter can also imbue the weapon with any one weapon special ability with an equivalent enhancement bonus less than or equal to his maximum bonus by reducing the granted enhancement bonus by the amount of the equivalent enhancement bonus. The item must have an enhancement bonus of at least +1 (from the item itself or from warrior spirit) to gain a weapon special ability. In either case, these bonuses last for 1 minute.