Doctor Strange in the Multiverse of Madness reveals that the Illuminati on Earth-838 defeated their version of Thanos, so what happened to their Infinity Stones? A flashback scene in the movie shows the aftermath of the battle on Titan with a very different outcome from the one that fans of the MCU are familiar with. It can be assumed that the Illuminati brought the stones and the gauntlet back to the Baxter Foundation, their headquarters on Earth-838, but since they are not mentioned once during Doctor Strange in the Multiverse of Madness, viewers are left wondering what happened to the stones after that fight.
In the MCU timeline of Earth-616, as depicted in Avengers: Infinity War, members of the Avengers and the Guardians of the Galaxy fight Thanos on his home planet of Titan, but with four Infinity Stones already in his possession, the mighty heroes are out-gunned and lose the battle. An alternate version of this scene appears in Doctor Strange in the Multiverse of Madness, where the Illuminati have succeeded in taking down Thanos with the sinister aid of a Darkhold-corrupted Stephen Strange. The defeated Thanos can be seen wearing the Infinity Gauntlet, housing the four stones he collected before making his way to Earth, including the power, space, reality, and soul stones, with the time stone still in the possession of the Sorcerer Supreme, and the mind stone presumably somewhere on Earth. After the fight, it would make sense for the Illuminati to take the stones back to Earth and keep them protected.
One story in Marvel comics alludes to how the Earth-818 Illuminati team might have protected the Infinity Stones. In the 2007 limited comic series “New Avengers: Illuminati," the members of the team collect all six Infinity Stones and, after failing to destroy them, they divide them up so that each Illuminati member can hide them, meaning they can never be used together again. Perhaps this is how they are protected on Earth-838. If the Illuminati shown in Doctor Strange in the Multiverse of Madness are protecting the stones, this means that they could easily avoid another Thanos-level threat, as well as prove their power as a superhero team.
This theory does raise some interesting questions. If the Illuminati were in possession of all six Infinity Stones, why didn’t they use them during the Scarlet Witch's attack against the Illuminati during Doctor Strange in the Multiverse of Madness? After Doctor Strange revealed Wanda’s intentions on Earth-838, the team underestimated the Scarlet Witch’s true strength, so perhaps they declined to use the stones as they didn’t feel the threat was great enough to warrant them.
It was shown that Mordo is the current Sorcerer Supreme on Earth-838, so it could be assumed that he is the protector of the time stone. Since he is the sole survivor of the Scarlet Witch massacre, it would be easy for him to simply reverse time and bring back all the members of the Illuminati. This would seriously lower the stakes presented in the film, though, as Wanda’s actions would have little to no consequence in their universe.
Since no information was given in Doctor Strange in the Multiverse of Madness about the whereabouts of the Infinity Stones in the universe of Earth-838, this is all purely speculation. It seems unlikely that Marvel would choose to revisit the Infinity Saga in the current and upcoming phases, preferring to keep the door closed on that chapter of the MCU. Despite this, there are many questions left unanswered about how the Illuminati actually defeated their version of Thanos, and what followed in the aftermath of the battle.
