This quest is not available in game.
Impsy in Felwood has asked that you bring him three Flawless Fel Essences originating from three distinct locations.
The Legashi Satyrs of Azshara hold the Flawless Fel Essence of their region. The Jaedenar Legionnaires of Jaedenar hold the Flawless Fel Essence of their region. The Felguard Sentries of the Blasted Lands hold the Flawless Fel Essence of their region.
Recover the Flawless Fel Essences and return to Impsy in Felwood.
If you're going to reanimate Kroshius, you're going to need Fel fire. I can make Fel fire but it's going to require some components.
You need to bring me flawless Fel essences from three distinct regions of the world.
The Legashi Satyrs of Azshara will have the first essence type; the Jaedenar legionnaires of Jaedenar the second type and the felguard sentries of the Blasted Lands the third.
Bring me back one of each essence type and I will create the Fel fire, allowing you to reanimate Kroshius.