Bane Of Argonnessen

Your Siberys dragonmark swirls as you battle dragons, empowering your weapons to deal greater harm.
Prerequisite: Any Siberys dragonmark.
Benefit: Any magic weapon you wield deals an extra 2d6 points of damage to dragons or any creature with the dragonblood subtype.
Special: A fighter can select Bane of Argonnessen as one of his fighter bonus feats.

Source: Dragonmarked