Yeah, on a bit of a Doc Strange kick lately...
The 5-page "Face-to-Face With the Magic of Baron Mordo" from STRANGE TALES #111 , the second Doctor Strange story, is reprinted here-in, introducing Doc's most persistent foe, the Ancient One's other student, who would figure into about half of the Ditko run of Doctor Strange.
The Ancient One's reluctance to see Mordo as evil until this point, given what we later see of Strange's origin, is kind of perplexing. Plus, just look at the guy (not that Doc looks like an angel at this point, with his far sharper features). In any case, this is where he finally makes his move to find out the last of his old teacher's secrets, sending his astral form to Tibet and using the Ancient One's servant to poison him. Doc gets worried when a message to the Ancient One doesn't get a response, so he also makes the astral journey, finding Mordo over his weakened Master. Fortunately, he's able to trick Mordo into racing back to his lair to protect his physical body, giving the Ancient One time to recover, and hopefully guard against further attack.
By the way, "How ironic that of both my pupils, only one fulfilled his promise, with the other --- Baron Mordo, threatens us so long as he lives". Um, how is that ironic? Plus, Doc's prediction that the loser of their next encounter would die isn't exactly spot on.
Still, these early 5-page quickies are fun, if less developed than the later tales when the feature got more pages. I especially like the glimpses into Mordo's dark, shadowy lair.