Foul-Smelling Sample

Foul-Smelling Samples are contained in Stinky Potions and Pots of Viscous Goop in Stormsong Valley or it also drop from the following mobs:
 * Briarback Geomancer
 * Briarback Lookout
 * Briarback Packmaster
 * Briarback Warcaller
 * Hulking Kraulguard

As a quest objective

 * Anger in a Bottle