Scattered around Draenor are four items belonging to the unfortunate mage -- his ring, staff, boots and hat. Each of these are in areas populated by level 100 mobs, so don't expect to get Vargoth right away, unless you like the idea of taking a lot of dirt naps. Vargoth's ring is located in the northwest section of Gorgrond, his boots are in the icy northeastern region of Frostfire Ridge, his staff is in a perpetually toxic swamp on the western edge of Nagrand, and his prized hat is in the heart of the worst of what lies in Shattrath City. Getting to the items is no easy task, but once found, each item begins a quest.
The items themselves are to be delivered to Khadgar's Servant -- yes, the slow-as-molasses tour guide from Burning Crusade
-- who has taken up residence in your garrison. Returning all four items reveals that Vargoth has been trying to affect a temporal shift between timelines, indicating that yes, we're in a separate timeline over on Draenor -- and Khadgar is none too happy about Vargoth's antics. However, combining all of the items together summons the image of Archmage Vargoth, who can then be talked to, and his quest completed. Grateful for your assistance, Vargoth wishes to extend his services to you via his powerful image, since he can't exactly be in Draenor in person.
To be clear, there are no indicators that Vargoth actually exists or is obtainable as a potential follower. You aren't pointed to his quests, they are simply items that you stumble across out in the world. This is just one example of the multi-layered nature of questing in Draenor -- certainly there are quest lines to follow and more than enough things to do. But players that take the extra steps to run around and simply see what they can find will often find themselves rewarded in meaningful ways. Personally, I'm glad to see Vargoth back in action, simply because he was such an oddly iconic figure from Burning Crusade
, despite being nothing more than a passing quest. Although his methods of getting involved with Draenor are sketchy, the expansion just wouldn't be the same without him.