It would be five years to the month (by our calendars) before Dr. Strange, Master of the Mystic Arts, would meet again with Dracula, Lord of Vampires, after having narrowly avoided a living death at the hands (er, fangs) of Dracula in
their first encounter. But just as Strange then had need of Dracula in order to save his servant, Wong, from the curse of the undead, their next meeting has their roles reversed, as this time it is Dracula who will need the skills of the Sorcerer Supreme as well as the might of his associates, the Defenders, in order to defeat the plans of the Six-Fingered Hand--a collective demonic entity whose goal is ultimately to merge Earth and Hell.
To that end, in order to remove the Defenders from possible interference, one of those demons, Puishannt, has empowered Gordski, one of Dracula's minor vampires, to be the new Lord of Vampires--even as no less than a dozen demons take possession of Dracula and drive him to physically attack Strange and the Defenders in the sorcerer's sanctum with the intent of slaying them. With the assistance of the Son of Satan in deciphering the truth, the attack fails--and Dracula is forced to depend on Strange to clear up the mystery of who had taken control of him, and why.
Having "eavesdropped" on the conversation between Gordski and Puishannt which reveals their complicity, Dracula and Strange realize that foiling this scheme is in all of their best interests, and reluctantly form a temporary alliance--though clearly, none of the Defenders are any happier with the decision than Dracula, an alliance made for the sake of expediency and, as Strange notes, common cause.

Clearly, Strange has brushed aside any surprise he might have felt at seeing Dracula among the living again (so to speak)--as well as, in light of the present danger from the Hand, any sense of responsibility he might have otherwise felt for finishing the task of dealing with Dracula's threat. It could be argued that the Defenders have no need to strike up an agreement with Dracula in order to battle one of the Hand (a point which, indeed, would be validated in the story's conclusion); but Dracula means to act no matter which way the pendulum swings here, and Strange and Hellstrom perhaps feel that choosing to meet one threat would allow the other to act unchecked.
In the end, the conflict demands that Hellstrom uphold his end of their agreement by conveying to Dracula valuable information that saves him from perishing with the rest of their foes. Yet, a little over two years later, Dracula and Strange would cross paths again, when Dracula's plans for ultimate power lead him on a quest to locate the Darkhold, a bound collection of parchments left on Earth by the demon Chthon--a demon the Avengers would encounter through the demon's possession of the Scarlet Witch, a woman who Strange now seeks out to help him reach the book first and thereby keep it out of Dracula's hands.
But how did Dracula learn of the Darkhold--and what's his interest in it?
For the answer, we'll have to flip the pages to yet another
Marvel Trivia Question
What's the official explanation for how vampires came to inhabit the Marvel universe?