The material below is Open Game Content from a 3PP Source
Aura strong evocation; CL 13th
Slot none; Price 8,810 gp; Weight 2 lbs.
As black as coal, this short sword grows more potent the farther it is kept from light. It acts as a +1 short sword when in dim light. In darkness, it acts as +2 short sword. When surrounded by supernatural darkness, such as in an area of deeper darkness, it acts a +2 short sword and bestows the benefit of the Blind-Fight feat to its wielder. In daylight or bright illumination, the sword temporarily loses all its magical enhancement bonuses and acts as a masterwork weapon, though it resumes its magical functions once it is no longer in the bright light.
Requirements Craft Magic Arms and Armor, deeper darkness; Cost 4,560 gp