You've worked your way up through the Brotherhood's corporate hierarchy, <race>. We have begun to look favorably upon you. Quite an accomplishment!
If you're interested in more work and earning more respect amongst us, listen up.
We can refine the fiery flux by adding a simple Dark Iron residue to the mix. The Dark Iron residue can be found in Blackrock Depths.
Keep the residue pouring in!
The entirety of this quest happens at Searing Gorge