Kill 10 Mageslayers and 10 Mana Seekers and return to Custodian Dieworth at Kirin'Var Village.
After the blood elves leveled Kirin'Var Village, they started the construction of a large building to the northwest. Without the expertise of the archmage, we can't say for certain what's going on there.
One thing is clear, though. The blood elf activities have unleashed a tide of ravenous mana elementals on the village. They seem drawn to the ruins of Wizard Row, wreaking further destruction. We cannot permit this to continue.