Marvel's "Doctor Strange" doesn't open in North America for another week, but director Scott Derrickson already has some ideas about what villain from the comic books he'd like to see in a sequel.

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“I really like the character of Nightmare and the concept that the Nightmare Realm is a dimension," he told IGN. "That’s early – that’s like the first Strange tale. I think that’s in the introductory episode of 'Doctor Strange,' and I always loved that."

Debuting at the same time as Doctor Strange, in 1963's "Strange Tales" #110, Nightmare is the sinister ruler of his own world within the Dream Dimension who influences, and torments, the dreams of humans as they sleep. Frequently depicted astride his demonic horse Dreamstalker, Nightmare has been a frequent foe of Stephen Strange, and has faced Ghost Rider, the Incredible Hulk and Spider-Man, among other Marvel superheroes. Nightmare and Doctor Strange are featured prominently in the new direct-to-DVD animated film "Hulk: Where Monsters Dwell."

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Asked by IGN why Nightmare wasn't included in "Doctor Strange," Derrickson replied, "We decided not to do that because that’s a bit of a complex idea to try to introduce everything we do introduce and introduce the idea of nightmares themselves as being a dimension. I hope somewhere down the line we do get to explore that because I think that’s super cool concept.”

While no sequel has yet been announced for "Doctor Strange," the character will appear in "Avengers: Infinity War," which arrives May 4, 2018.

"Doctor Strange" is the story of world-famous neurosurgeon Dr. Stephen Strange whose life changes forever after a horrific car accident robs him of the use of his hands. When traditional medicine fails him, he is forced to look for healing, and hope, in an unlikely place—a mysterious enclave known as Kamar-Taj. He quickly learns that this is not just a center for healing but also the front line of a battle against unseen dark forces bent on destroying our reality. Before long Strange — armed with newly acquired magical powers—is forced to choose whether to return to his life of fortune and status or leave it all behind to defend the world as the most powerful sorcerer in existence.

Opening Nov. 4, "Doctor Strange" stars Benedict Cumberbatch, Chiwetel Ejiofor, Rachel McAdams, Benedict Wong, Michael Stuhlbarg, Benjamin Bratt, Scott Adkins, Mads Mikkelsen and Tilda Swinton.