The dark mage is a Zamorakian mage who can be found close to the entrance of the Underground Pass in West Ardougne. He is found in a stone brick tower slightly east of the Underground Pass, which is in better shape than most of the other buildings in the town.
When asked about fixing Iban's staff, he will shout "Almighty Zamorak! The Staff of Iban! This is truly dangerous magic, traveller. I can fix it, but it will cost you, the process could kill me." and then demands 200,000 coins. Upon fixing it he will comment: "You be careful with that thing!"
The dark mage looks almost exactly like a Disciple of Iban, the only difference being that the disciples are paler.