Crystal of Mastery (3.5e Equipment)

Crystal of Mastery
The crystal of mastery lights up when the weapon or shield is picked up, its clear crystal insides filled with a unique arcane fingerprint for every user. You feel like you've known this item your entire life, and it moves as easily as moving your arm. These crystals can be attached to either weapons or shields equally well.

You become proficient in the weapon or shield equipped with this crystal (and only this weapon; i.e. if you pick up two kukris which you are not proficient and one has a crystal, you are only proficient in the crystal-bearing weapon).
 * Least

As the least crystal, and you have a minimum of medium BAB with attacks when using this a weapon or shield with this crystal.
 * Lesser

As the lesser and least crystals, and you have full BAB with attacks when using this a weapon or shield with this crystal.
 * Greater

Aura: Faint (DC 17) transmutation Price: Cost::3,000 gp (Least), Cost::9,000 gp (Lesser), Cost::27,000 gp (Greater)