Warning: Major SPOILERS Ahead For Doctor Strange in the Multiverse of Madness!
Doctor Strange in the Multiverse of Madness makes Marvel history, becoming the first film in the MCU to feature the iconic Illuminati, which has a long and storied history in the comics. This council is revealed to be an institution of Earth-838, where mutants, Inhumans, the Fantastic Four, and more are established superheroes that have come together to decide the fate of their own universe.
The Illuminati is comprised only of incredibly powerful beings, each of whom represents a major subject of people on the planet Earth. As such, each member of the Illuminati gets a chance to display their battle prowess in the film, particularly when Wanda Maximoff (Elizabeth Olsen) infiltrates their compound. In a desperate bid to stop the Scarlet Witch, each of these falls in battle, with some going down far easier than others.
Black Bolt
In a surprising twist, Anson Mount reprised his role from the failed ABC series The Inhumans, as King Blackagar Boltagon, the leader of the Inhumans in the Marvel comics. Blackagar, otherwise referred to as Black Bolt, is an Inhuman with the power to decimate anything with the intense soundwaves generated from his mouth, making him a formidable foe.
While Black Bolt is extremely powerful, as evidenced by the brief scene in which he executes Earth-838's Doctor Strange for his crimes, he is taken out quite quickly by the Scarlet Witch, who merely erased the Inhuman's mouth, causing his subsequent screen to blow up his own brain. Black Bolt may have been able to stand his ground against Wanda in a proper battle, but unfortunately, he never got the chance to prove as much.
Doctor Strange
The Doctor Strange (Benedict Cumberbatch) of Earth-838 is not present for the events of Multiverse of Madness, as he lost his life during his universe's battle with Thanos. It is later revealed that the other of the Illuminati deemed it necessary to have this version of Strange executed after he recklessly misused the Darkhold to help his team defeat Thanos.
While this Strange is never depicted in combat, it may be the case that he was significantly less powerful than his Earth-616 counterpart, who, though similarly unable to defeat Thanos, managed to use his powers to find the one future where the Titan was defeated, circumventing Thanos's ultimate plan and restoring order to the universe. While Earth-838 Doctor Strange may never see battle on the big screen, his legacy of weakness persists after his decease.
Mister Fantastic
Multiverse of Madness fulfilled many fans' wishes by including a cameo from John Krasinski as Dr. Reed Richards, thereby implying that Mister Fantastic may be played by Krasinski in the MCU as well. This version of Richards is noted as the leader of the Fantastic Four, husband of Susan Storm, and father to at least two children.
Although the mere presence of Mister Fantastic in an MCU property is enough to keep fans satiated for a time, this variant unfortunately doesn't last very long in battle with Wanda. Though he has the ability to stretch his body to incredible lengths, it only takes a few moments for Wanda to suspend him completely before shredding him to pieces.
Karl Mordo
Karl Mordo (Chiwetel Ejiofor) is the Earth-838 counterpart to Doctor Strange's archnemesis from his own homeworld. This version of Mordo replaced his universe's Strange after his death, becoming both the Sorcerer Supreme and the Masters of the Mystic Arts' delegate in the Illuminati. He deals primarily with Doctor Strange, who he claims had been his friend on his world, though the MCU's Strange seems wary of such a possibility.
Mordo is the only member of the Illuminati not to face off against Wanda Maximoff and therefore becomes the council's last surviving member by the film's end. The sorcerer does engage in battle against the captured Strange, however, wherein he proves to be rather headstrong and arrogant, allowing himself to be fooled into freeing his opponent, who escapes shortly thereafter.
Professor X
Sir Patrick Stewart once again reprises his role as Professor Charles Xavier from Fox's X-Men films, with this appearance becoming his eighth as the character. Xavier is the head of the Illuminati on Earth-838 and is also assumedly the leader of the X-Men in his world, who deals with Doctor Strange directly, telling him the truth of his fate as a destroyer of his own universe.
The version seen in Multiverse of Madness may not be one of the most powerful variants of Professor X we've seen, but he still proves to be a remarkably strong mutant with the ability to briefly incapacitate the Scarlet Witch herself before succumbing to her incredible might. For several moments, Professor X actually appears to be winning against Wanda, only for it to be revealed that she has been fooling him all along, leading to the rageful Avenger psychically snapping the professor's neck, killing him instantly.
Captain Carter
Hayley Atwell reprises her role of Peggy Carter, but this time with a twist. Adopting the storyline from What If...">Captain Carter, a variant whom some fans even prefer over Captain America himself.
Despite not having the incredible power of some of her compatriots, Captain Carter quickly asserts herself as one of the most skilled fighters among the Illuminati, outlasting both Black Bolt and Mister Fantastic in the battle with the Scarlet Witch. This universe's first Avenger goes hand-to-hand with her powerful combatant, holding her own for quite some time before eventually being killed with her own shield.
Captain Marvel
Lashana Lynch returns as Maria Rambeau, only this time it was she and not Carol Danvers who became the superhero known as Captain Marvel. This version of the character appears to have the same set of powers and abilities as the Earth-616 Carol Danvers, which certainly comes in handy against the powerful threat of the vengeful Scarlet Witch.
Of the initial battalion sent to fight Wanda, Captain Marvel is the last to be killed and was the only member of the Illuminati up until that point to actually nearly defeat her opponent. Wanda actually sustained several blows in her duel with Rambeau, eventually desperately dropping a towering statue upon her enemy's head in order to bring the fight to a quick end.