The Emerald Nightmare: Rage Fire
The Emerald Nightmare: Rage Fire is a raid quest for level 45. It is step 32 of 33 in the Legion Alchemy storyline. The quest's turn-in marker is in Dalaran at 44.1, 28.7. It rewards 6,150 experience.
Description
Now that we have all the ingredients assembled, we need one last thing.
The fire of my forges burn hot, but not hot enough to work these ingredients into glass. For that, we need more heat. The heat of a dragon, to be exact.
I'm aware of one that has emerged from the Emerald Dream in a corrupted state. Corrupted or not, a dragon's heart burns with enough heat to melt the strongest of materials.
Bring me its heart and you'll have your conduit.

