Marvel Super Heroes Adventure Gamebook #4
From back cover:
You are Doctor Strange, Sorceror Supreme, sworn to protect Earth at all costs. The six sorcerors from the realm of Trofane manifest themselves all at once in the body of your manservant, Wong. They bring terrible news: Earth is about to become a battleground more deadly than any human conflict could create. This is a fight between different dimensions and you must act immediately if Earth is to be saved from total annihilation!
MARVEL SUPER HEROES Adventure Gamebooks are based on TSR, Inc's popular MARVEL SUPER HEROES role-playing game, but you needn't know the game to enjoy the exciting adventure in this book. All you need to do is get one standard, six-sided die, summon your cloak of levitation and Eye of Agamotto, and assume the role of Doctor Strange as he seeks to save Earth from certain destruction in THROUGH SIX DIMENSIONS.