Scalebane Bottle

Scalebane bottles are extremely helpful tools when fighting dragons with high natural armor bonuses. When the bottle is opened, it sends forth a dull gray ray of magic, weakening the strength of a creature's scales. Although the bottles are effective against all creatures that have natural armor, they were designed to combat dragons.
Each scalebane bottle is made from Cormyrean glass, wrapped in snakeskin, and capped with a small cork. An individual who holds one can feel faint vibrations within. In order to remove the stopper from the bottle, its wielder must say the command word "Derynax." The wielder then points the bottle toward the target creature and removes its cork.
Once per day, the wielder can uncork the bottle and direct a ray of magic at a creature up to 60 feet away as a ranged touch attack. If the target is struck, it takes a -10 penalty to natural armor for 10 minutes. This penalty cannot reduce the creature's natural armor bonus below 0, nor does it have any effect on enhancement bonuses to natural armor (such as that granted by a barkskin spell). The target is not entitled to a saving throw, but the ray is subject to spell resistance; the wielder rolls 1d20+15 and must beat the creature's spell resistance.
Strong transmutation; CL 15th; Craft Wondrous Item, scale weakening; Price 10,800 gp; Cost 5,400 gp + 432 XP; Weight 1 lb.
Source: Dragons of Faerûn