Mux Manascrambler is a level 60 quest giver located in Gadgetzan in the contested territory of Tanaris. He can be found in a house in the northeast corner of the city, near the female gnome with the egg machine.
He starts the following quests:
See List of Tanaris NPCs.
He will hand out additional Extra-Dimensional Ghost Revealer's after completing the quest the first time if needed.