Based on the trailers, Doctor Strange in the Multiverse of Madness will reunite the Scarlet Witch with at least versions of her sons Billy and Tommy. Her trip through the multiverse will also be an opportunity for the movie to introduce some of the best Scarlet Witch characters from Marvel Comics who aren't yet in the MCU. Among them are some of the most significant characters in Marvel lore.
Wanda Maximoff's comic book history is complicated and full of twists and turns. They involve a number of the most powerful figures in Marvel Comics, like Magneto, who at times in continuity has been her father. They also include prominent Avengers like Wonder Man who have yet to make it to the screen, but thanks to Wanda's growing importance in the MCU, are likely to in the future.
Mephisto
Many MCU fans speculated Mephisto would make his MCU debut in most powerful magical beings in Marvel Comics, has deep and tragic ties to the Scarlet Witch.
Her children were actually created from fragments of his soul, making him one of the best Scarlet Witch comics characters not in the MCU. His prominent role in the cosmic and mystical realms of the Marvel Universe makes him a lock for the cinematic universe.
Master Pandemonium
A key figure in the tragedy of Billy and Tommy Maximoff is the villain Master Pandemonium. He made a deal with Mephisto to recover his lost arm, and that led ultimately to his recovering the missing fragments of Mephisto's soul in the form of Wanda's children.
Master Pandemonium's role in the shocking twist of the twins' origin makes him one of the best Scarlet Witch comics characters not in the MCU. He could still appear if Mephisto does, though his connection to the twins is very likely to change from the comics.
Immortus
Immortus is one of the most powerful variants of Kang the Conqueror and he plays a key role in the story of the Scarlet Witch in the comics. He discovers she's a Nexus Being, a one-of-a-kind figure of truly cosmic power in the Marvel Universe.
His attempts to exploit her for his own ambitions will surely play out in the MCU. As both Kang and the Scarlet Witch both grow in power in the MCU, their paths are very likely to collide in the near future, maybe even as soon as Doctor Strange in the Multiverse of Madness.
The Whizzer
The Whizzer is one of the unlikeliest Scarlet Witch comic book characters not in the MCU, but he is one of the most significant in of her backstory. In the beginning, this Golden Age superhero was Wanda and Pietro Maximoff's father.
The Whizzer and Miss America, both World War II characters associated with The Invaders, were later retconned out of any family connection to the Scarlet Witch. His role with The Invaders could still land him in the MCU if the franchise goes there, though.
Doctor Doom
Comic book fans know Doctor Doom is one of the greatest Fantastic Four villains in the comics. He's also a major figure in Wanda's life, being her romantic partner in a very unusual sense for a brief period in The Children's Crusade storyline from the early 2000s.
Doctor Doom's power in magic as well as his role as one of the premier villains of the entire Marvel Universe make him one of the best Scarlet Witch comics characters not yet in the MCU, but he certainly soon will be, perhaps even in Phase Four.
Chthon
Chthon is the source of Chaos Magic in the Marvel Universe and he is the source of Wanda's power with it. He ranks high among the best Scarlet Witch comics characters not in the MCU for choosing her as his dark avatar when she was just a child.
The Scarlet Witch is exploring Chaos Magic in the MCU through the Darkhold, which is a mystical tome written by Chthon to house his darkest spells. It's likely he will play some role in the MCU soon, and perhaps even in the movie.
The High Evolutionary
The High Evolutionary is a significant villain in Marvel Comics, first appearing in The Mighty Thor #133 back in 1966. While he's fought most of the Marvel Universe, he's one of the best Scarlet Witch characters in the comics due to his role in her origin.
Though her parentage has shifted again and again, the High Evolutionary played a role in retconning Wanda away from being a mutant. He claimed to have performed experiments on her parents, something that could still play out in the MCU.
Bova
Another key figure in Scarlet Witch's origin is Bova. A product of the High Evolutionary's experiments at Wundagore Mountain, this unusual character has been a constant friend and ally to the Maximoff family through the generations.
Her role in Scarlet Witch and Quicksilver's birth makes her one of the best comics characters not in the MCU. She still could be a factor in live-action if the MCU goes to Wundagore Mountain, which it might in Doctor Strange in the Multiverse of Madness.
Wonder Man
Wonder Man plays a major role in Marvel Comics as the Scarlet Witch's love interest as well as the spiritual father in some respects of The Vision, whose mind was copied from Wonder Man by Ultron. Wonder Man's complicated role in their romance makes him one of the best Scarlet Witch comics characters still not in the MCU.
He's been a member of the Avengers since the 1960s and has been a part of some of their biggest stories in the comics, making his absence from the MCU significant. He could still play a role, though it would be vastly different from the comics.
Magneto
Perhaps the best and most important comics character related to the Scarlet Witch not in the MCU is Magneto. Scarlet Witch first appeared as one of his acolytes in The Brotherhood of Evil Mutants in X-Men #4 and was later revealed to be his daughter.
Though that backstory was changed in the comics, it seems to be coming back around in favor as Wanda res the House of Magnus in current comics. Her familiar connection to Magneto could become a factor in the MCU as soon as Doctor Strange in the Multiverse of Madness given the fact that Professor X appears to be playing a role in the movie.
