Doctor Strange : Sorcerer Supreme #6 (Key: 1st App. of Mephista)
Baron Mordo had promised a soul to both Satannish and Mephisto, so Doc has to deal with them, Mephista and the Sons of Satannish until he is forced to enter Agamotto's realm.
1st Appearance of Mephista; Origin of Baron Mordo
Estimated Condition: VF/NM