OR: "Dr. Strange, Hiker of the Mystic Arts"
The thought of Michael Golden handling the artwork for the forty-page What If story featuring Baron Mordo as the Master of the Mystic Arts would be enough to spur even the Dread Dormammu into picking up a copy. Alas, Mr. Golden took care of just the cover art. Still, one look at the exquisite splash page for the issue has one thinking that artists Butch Guice (née Jackson Guice) and Sam Grainger are the next best thing, eh?
Mordo's turn at being the Ancient One's choice to succeed him is an interesting premise to explore, though we don't really need the Watcher to get that ball rolling: Basically, something must happen (or not happen) to prevent Strange from taking Mordo's place as the Ancient One's disciple. But Mordo actually wanting to be worthy of the Ancient One's teachings is a new twist that only Uatu could see coming.
(Of course, if you're under the impression that those tentacles somehow played a part in Mordo becoming the model student, you get a complimentary copy of the Book of the Vishanti! (Not really!) )
From here, things progress for Mordo as they did for Strange--except for writer Peter Gillis feeling the need to plant a seed in our minds that something is up here. (It occurs to me that if Wong distrusts Mordo, surely the Ancient One would still have misgivings, but what do I know.)
Soon enough, Mordo's baptism of fire arrives in the form of Dormammu's intent to invade our dimension. Unlike Strange, however, the shrewd Mordo decides to forcefully secure the aid of another denizen of the Dark Dimension, Clea, in order to enact a plan to free a menace from captivity that even Dormammu must drop everything to defend against.
And what of Strange? He's decided to use his new lease on life to become an instructor at a New York medical school--yet unknown to him, he has also fallen prey to a powerful entity who uses a person's dreams to inflict suffering, a foe he would have battled in our reality as "the Master of Black Magic."