Despite merely serving as a backdrop for Scarlet Witch, the presence of the secret Illuminati in Doctor Strange 2 is enough to thrill fans.
Note: This article contains spoilers for Doctor Strange in the Multiverse of Madness.
Doctor Strange in the Multiverse of Madness has brought forth many intriguing details related to Marvel comic characters, artifacts, and a myriad of major events. Among them, Illuminati stands out - a clandestine organization that gathers the mightiest superheroes to decide the fate of the world. Unfortunately, the screen time of Illuminati (belonging to the Earth-838 reality) in this film is too short, and they only play a secondary role in Strange's multiverse adventure.
So how did the Illuminati come into existence and what impact do they have on the Marvel universe?
The origin of the Illuminati in comic books

As previously mentioned, Illuminati is a clandestine organization comprised of the world's most influential superheroes: Sorcerer Supreme Stephen Strange; King of the Inhumans, Black Bolt; X-Men founder and mutant rights activist, Charles Xavier; Emperor of Atlantis, Namor the Sub-Mariner; founding member of the Fantastic Four, Reed Richards; and founding member of the Avengers, Tony Stark. These 6 superheroes have collaborated to 'mold' and shape the world's condition.
Tony Stark is the one who proposed the idea of Illuminati to T’Challa (Black Panther) after the Kree - Skrull war ended. Stark aimed to establish a powerful organization capable of uniting all different superhero teams to be prepared for similar threats in the future. However, Stark's idea was narrowed down, with a significant decrease in the number of members. These members would secretly share information and collectively decide to address major issues, including the return of Sentry. However, T’Challa decided not to join Illuminati.

Illuminati operated smoothly until Tony Stark deceived Hulk and sent the green giant into space, to a distant planet. This decision led Namor to leave the organization due to disagreement. Meanwhile, Charles Xavier disappeared after the House of M event. Stark attempted to salvage the situation by drafting the Superhuman Registration Act to prevent future civil wars, but most of the remaining members disagreed. Illuminati officially disbanded.
However, when the Avengers discovered a Skrull impersonating assassin Elektra, Stark stepped up to reassemble the organization. However, while they were still struggling to figure out how to deal with the new problem, they were immediately attacked by another Skrull morphed into Black Bolt. Although they successfully thwarted the alien race's plot, seeds of doubt were sown among the superheroes of Illuminati, causing them to no longer trust each other as before.
Illuminati in the MCU

In Doctor Strange in the Multiverse of Madness, Strange had the opportunity to encounter the Illuminati of the Earth-838 universe. Similar to the comics, this organization secretly votes and makes decisions on the most serious issues, such as the punishment for Strange and America Chavez for multiverse travel that could cause invasive phenomena, potentially endangering at least one reality from complete destruction. Unlike Earth-616, Illuminati here has been active for quite some time, even before the infinity war with Thanos erupted.
Besides, the members of this organization also underwent significant changes compared to the comics. Stephen Strange, who once wielded both the Darkhold and Vishanti books in Earth-838, is the founder of Illuminati. He's the one who ventured into other universes to find a way to defeat the mad Titan, ultimately leading to the collapse of an entire reality. Illuminati then decided to kill Strange to prevent the dangers that his arrogant, action-prone nature could cause in the future.
Other members of this organization include Baron Mordo - a close ally (not an enemy) of Strange in the Earth-838 universe; Charles Xavier, the X professor from the previous X-Men films; Peggy Carter/Captain Carter, who was injected with super-soldier serum instead of Steve Rogers; Maria Rambeau - Captain Marvel of Earth-838; Black Bolt, the leader of the Inhumans, who can bring down an entire building with just a whisper; and Reed Richards of the Fantastic Four, known as the 'smartest man in the world'.
The Future of Illuminati in the MCU

The appearance of the secret society Illuminati in Doctor Strange in the Multiverse of Madness indeed thrilled many fans, but that joy lasted only a few minutes. Most of the members of this organization were then 'wiped out' and slaughtered by Scarlet Witch in various gruesome ways.
However, don't forget that this is the Illuminati of the Earth-838 universe, while the main timeline of the MCU is Earth-616. Not ruling out the possibility that after the events of the multiverse journey, Doctor Strange will consider and establish his own Illuminati for his universe. Many future projects of Marvel Studios support this hypothesis, including the Secret War series, as Skrulls invade Earth; Fantastic Four, bringing Earth-616's Reed Richards to the big screen; The Marvels, as Captain Marvel and Monica Rambeau reunite; and especially the X-Men mutants, who are closer to this cinematic universe than ever before.
According to Collider