Demon Bane Weapon

The Gates of Hell (Dice Freaks)
Grimoire of Cosmic Entities Volume One By Eli Atkinson, William Church and Serge W. Desir, Jr.
Original Concept by Serge W. Desir, Jr.
Full netbook can be found on the following website
Dicefreaks d20 Community

A demon bane weapon excels at attacking demons. Against such foes, its effective enhancement bonus increases by +3, and it deals an additional +3d6 points of damage. Bows, crossbows and slings so crafted bestow the bane quality upon their ammunition.

Moderate Conjuration; CL 12th; Craft Magic Arms and Armour, Summon Monster I; Price +1 bonus.