Doctor Strange in the Multiverse of Madness

America Chavez, a teenager who can punch holes between universes and cannot control it, is being hunted. The hunter is Wanda Maximoff, corrupted by the Darkhold, trying to steal America's power so she can travel to a universe where her children exist.

Strange takes America to Earth-838, where he meets the Illuminati: Mordo, Peggy Carter as Captain Carter, Blackagar Boltagon (Black Bolt), Maria Rambeau as Captain Marvel, Reed Richards (John Krasinski), and Professor Charles Xavier — Patrick Stewart, in the animated-series wheelchair. Wanda kills all of them.

America turns the tables by giving Wanda what she wanted — a meeting with the 838 versions of her children, who are terrified of her. Confronted with that, Wanda uses her power to destroy every copy of the Darkhold across every universe, then collapses Mount Wundagore — the temple built on the Darkhold's origin site — on top of herself.

She is presumed dead.

No body is shown, and a scream is audible from the rubble, so Marvel deliberately left it ambiguous. Elizabeth Olsen is not listed for Doomsday.

Key concepts introduced: incursions — when two universes collide, one or both are destroyed. Dreamwalking — possessing a variant of yourself.

Incursions are the most likely mechanism for whatever Doom does.