Warning! SPOILERS for Doctor Strange in the Multiverse of Madness.
Doctor Strange in the Multiverse of Madness established new rules for dreams in the MCU’s multiverse, hinting that a major Doctor Strange supervillain’s origin has already been changed. The classic Marvel villain Nightmare rules the Nightmare Realm, a portion of another plane of reality called the Dream Dimension in the Marvel Comics universe. Doctor Strange 2 changed the meaning of dreams in their relation to the multiverse, and thus Nightmare will need a new origin if he appears in the MCU.
Debuting in a 1963 issue of Strange Tales, Nightmare is a god-like entity whose rules over a portion of the Dream Dimension, which is formed from the collective unconscious of humanity. Although Nightmare is one of the Marvel Comics universe’s most powerful beings, his powers are limited. Nightmare is invincible as long as there are beings who sleep, but he lacks power over those who are awake. Nightmare, along with Baron Mordo and Dormammu, is one of Doctor Strange’s greatest enemies.
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Nightmare was rumored to be the villain of Doctor Strange 2, but this ultimately turned out to be Wanda Maximoff, whose title of Scarlet Witch now symbolizes her corruption rather than her heroism, as depicted in the comics. Dreams in the MCU have different properties, representing the experiences of one’s variant in another reality instead of a temporary and (usually) harmless visit to the Dream Dimension. With this in mind, an MCU version of Nightmare would need to have his origin altered, making him a dangerous entity who menaces the entire multiverse, making him similar in a sense to the film’s
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