Maleficent

Hope Sora, Donald Duck and Goofy visit the worlds like the same of Toy Box where they'll see Woody and Buzz again, Arendelle to see Anna, Elsa, Olaf, Kristoff and Sven again, Pride Lands to see Simba, Nala, Timon, Pumbaa and Rafiki again, Monstropolis to see Mike and Sulley again and Mount Olympus to see Hercules, Meg and Phil again. And also new worlds like Chinatown, Toronto where they'll meet Mei Lee, Ming Lee and Mei's friends, Montunui where they'll meet Moana, Maui and Heihei, Colombia, Mi Encanto where they'll meet Mirabel, Antonio, Alma Abuela, Bruno and the Madrigal family, Metroville where they'll meet The Incredibles, New Orleans where they'll meet Tiana and Land of the Dead where they'll meet Miguel and Héctor.

What do U think might happen if she gets the "Book of Prophecies"?

I could see Doctor Doom, Kingpin(Spider-Man: TAS), and Loki(or Hela) myself. Kingpin could have members of the Sinister Six(Doc Ock, Mysterio, Vulture, etc.) as his allies, similar to the Hyenas or Lock, Jock, and Barrel.

I do not see Thanos's goals, MCU or comics, really aligning with what Maleficent wants. Similar issues with Galactus, who is not really a villain but rather an important part of the universe.

Magneto is not evil and he only wants mutants to prosper by any means necessary. I can't really see him siding with someone who wishes to engulf all the worlds, and by extension all mutants, in darkness.