In Black Panther: Wakanda Forever, Namor the Sub-Mariner makes his MCU debut as Atlantis goes to war with Wakanda, effectively laying the foundation for the formation of a new Illuminati in Earth-616. Doctor Strange in the Multiverse of Madness' Illuminati appearance, though short-lived, was the first time for the MCU to tackle the concept of a superhuman/mutant council governing the world. Earth-838's Illuminati is actually inspired by a much older and clandestine super team.
Making their first Marvel Comics appearance in 2005's New Avengers #7, the original Illuminati was comprised of Iron Man, Namor, Doctor Strange, Reed Richards, Black Bolt, Professor Charles Xavier, and Black Panther. Following the Kree-Skrull War, Tony Stark realizes that each of these heroes had information about the alien races prior to the war spilling onto Earth. Given their collective resources, they could have prevented the crisis before it happened, so Iron Man proposes to form a superhuman government for this express purpose. Everyone refuses, stating their own reasons for why it's a bad idea. However, they also agree to regularly meet in secret, leading to the creation of Marvel Comics' Illuminati. Only T'Challa refuses to participate, insisting that it won't end well. Indeed, the Illuminati end up enabling the Skrull invasion of Earth, pushing for the Superhuman Registration Act (which inspired the Sokovia Accords), and even banishing Hulk to space. As Namor tells the Illuminati after he almost drowns Stark for thinking that it's a good idea to banish his fellow Avenger, Black Panther was right. That said, despite its faults, the Illuminati eventually becomes crucial to preventing Earth and even the entire Marvel Universe from being
Read more on screenrant.com