Fully investigate the Blood Furnace and then report to Nazgrel at Thrallmar in Hellfire Peninsula.
[class], you must gather a group to investigate the Blood Furnace inside Hellfire Citadel at once!
The magical scrying that we have at our disposal indicates that something unnatural is occurring in there. But a powerful force inside is blocking any detailed arcane investigations, so it must be very important.
You should expect heavy resistance - no other mission that we've sent in there has ever returned!
Scout it entirely and then report back to Nazgrel, advisor to Thrall, with what you witness.