Oil of the Lamia

Said to have been created by an evil lamia wizard, this concoction makes magic items more powerful.

Book of Vile Darkness 3.5
By Monte Cook

When applied to a magic item that produces an effect requiring a foe to make a saving throw, the oil increases the DC of the saving throw by +2 if the foe is of good alignment. The oil lasts for 1 hour. The oil is held in a small flask and will coat one item, no matter the size.

Caster Level: 7th; Prerequisites: Brew Potion, dispel evil; Market Price: 2,000 gp; Weight: 1 lb.