Seven Spice Black Powder
Seven Spice Black Powder is a secret mix of herbs and spices whose composition is a closely guarded secret in Agatea. Used in the local cuisine, it is a key component of Grimchi, a local delicacy based on cabbage fermenting in vinegar.
The powder is volatile, unstable, and possibly very, very, explosive. It is not thought to be an ingredient of Wow-Wow Sauce - yet. But if Mustrum Ridcully got to hear of it, you can be sure that it would be. The Exothermic Alchemy labs at the Assassins' Guild School would also take a professional interest, as well as its newly-formed Domestic Science department. The canonical Miss Smith-Rhodes would be sure to take a keen interest.
For now, the only clue it ever appeared on the Central Continent are seven very large craters in the ground in the vicinity of Seven Bangs, the people who brought it there having vanished into thin air. Perhaps it is safer this way.