Doctor Strange in the Multiverse of Madness sent shockwaves throughout the Marvel Cinematic Universe.
As the Scarlet Witch explains in trailer footage, When the good doctor "breaks the rules," he's seen as a hero, but when Wanda does it, she becomes "the enemy."
Later in Multiverse of Madness, tapping into the pages of the Darkhold in order to bring an end to defeat Scarlet Witch. Unlike giving up the Time Stone or instigating the memory spell, this enacted cheat code comes with direct consequences.
While Strange is perusing the New York City streets, he is overcome with terror and collapses to his knees. The sorcerer then jolts up, opening a new third eye on his forehead. The repercussions from his Darkhold usage don't end there, as Strange is confronted by a debuting A-Lister in the film's first post credits scene.
Doctor Strange in the Multiverse of Madness sent fans into the scrolling credits with the first Marvel Cinematic Universe appearance of Clea, played by Charlize Theron. The atomic blonde-haired magic user dropped a bombshell on Strange by noting he caused an "incursion," before asking that he join her down the fury road into the Dark Dimension.
Charlize Theron's Clea has major implications for the Doctor Strange franchise moving forward. This is a comic character that wears plenty of hats. On the page, Clea has been Doctor Strange's student, significant other, and even successor. She is the offspring of Prince Orini and Umar, the sister of Dormammu, that makes her Dormammu's niece.
Unlike Nebula and Shang-Chi, Clea does not hate her villainous parents: she embraces it. Clea worships Dormammu and even becomes the Sorcerer Supreme of the Dark Dimension.
Despite her mob ties, Clea is not all evil. As mentioned, she eventually falls in love with Doctor Strange after betraying Dormammu. Without a dimension to call home, Strange would take Clea under his wing in New York City. The good doctor would even teach Clea his mystical ways at the Sanctum Sanctorum, and when he eventually met his end, Clea would take his place as Earth's Sorcerer Supreme. She would even honor his memory by adopting the Strange surname.
The post-credits implications go beyond the debuting character. Clea claims the events of Multiverse of Madness caused an "incursion." Incursions are a collision of two Earths. They are triggered when one universe's character kills his or her own Variant. In Doctor Strange 2, Earth-616's Doctor Strange kills Sinister Strange, impaling the evil iteration on a fence outside the Sanctum Sanctorum. If the MCU's incursions have the same definition as they do in the comics, Marvel fans could be looking at a colossal consequence comes in Doctor Strange 3.