In Dr. Strange #59 (June 1983), the master of the mystic arts learned that Dracula was again at large. The disturbing news jogged the sorcerer's memory of his initial encounter with Dracula in Dr. Strange #14 (May 1976).
Seven years in real time elapsed between the publication of those two issues, but characters within the world of comics tend to experience time at a slower rate. According to Dr. Strange's account in #59, barely two years had passed since he met the Lord of Vampires in #14.
Yet only after summoning the all-seeing Eye of Agamotto from his mystic amulet did Dr. Strange recall a more recent encounter from Defenders #95 (May 1981), when Dracula had invaded the Sanctum Sanctorum under the influence of the Six-Fingered Hand. How could Dr. Strange have forgotten such a pivotal event? The sorcerer suspected that Mephisto was responsible for obstructing his memory and numbing his awareness of Dracula.