The Cult And The Curse 1st appearance of (Doctor Strange "Blue Costume")
The Sons of Satannish have taken Doctor Strange's cloak and amulet, and exiled him and Clea to a hostile dimension. A "protoplasmic shape" captures Clea, who cannot cast spells. Strange pursues it after escaping one himself.
Meanwhile, Asmodeus has the Book of the Vishanti, but it vanishes, as do the cloak and the amulet. He and the Sons of Satannish use the Trance of Transferal, which gives the cultists' powers to Asmodeus. As thanks, he sends them to oblivion. He then takes the form of Doctor Strange.
Back in the alien dimension, Strange frees Clea from the shape. During a brief rest, we find that he cast invisibility on his amulet and transferred much of his power into his cloak, expecting that he would lose the first encounter with the cult. He let the cultists take illusory doubles of both items.
Vines attack them and envelop Strange. He sends his amulet to retrieve his cloak, which he left in a graveyard on Earth. With his full powers, he tries to return to Earth but is prevented by the fact that Asmodeus now has his form. He therefore changes his form, into a bald blue figure, and hastens to the Ancient One's retreat. There he duels with Asmodeus, whose heart fails. Strange removes his mask and finds Doctor Benton, a former colleague. He has arrived a moment too late, though, for Benton has already summoned Ymir and Surtur.