|Dust of envy|
Source: More Magic of Thassilon, pg(s). 1
It is believed that dust of envy was first developed by Runelord Belimarius during the ancient Thassilonian empire. Certainly samples of it are still found from time to time in the ruins of the domain of Edasseril in modern Varisia.
This blue dust is generally encased in a crystal phial and carried on a chain around the neck. When the casing is shattered the dust spreads out and acts as a dispel magic spell, which only targets spells of the evocation and necromancy schools.