A secret seventh Infinity Stone could be introduced to the Marvel Cinematic Universe in The Eternals. Throughout the first 11 years of the MCU, the Infinity Stones have become central to the overall narrative. Collecting the six stones was Thanos' main goal, and he accomplished that in Avengers: Infinity War, while the Avengers then had to obtain them to reverse his actions in Avengers: Endgame. These artifacts are so crucial to the main story that Kevin Feige called this stretch for the MCU the Infinity Saga.
The MCU has explained that the six Infinity Stones predate the universe itself and are critical to the natural flow of time. However, we've only seen a glimpse of the origins and early usage of the Infinity Stones. That could change with The Eternals, a new cosmic franchise that could span thousands of years and show new parts of the MCU's history. We've theorized that the Infinity Stones creates the Eternals themselves (a group of incredibly powerful, genetically enhanced individuals). If the Infinity Stones are involved in The Eternals' story in any way, there is the chance that the movie could introduce the little known seventh Infinity Stone.
The introduction of the stone, also known as the Ego Stone, in the MCU is the subject of Screen Rant's latest video. The Ego Stone has a history in the comics with Sersi, one of the main characters of The Eternals, which could make the new movie the perfect opportunity to introduce it to the MCU. For those who aren't aware, the Ego Stone was created during a Marvel Comics crossover with their then-recently purchased company Malibu Comics. The crossover saw the Avengers fight the superteam known as Ultraforce as Loki and Grandmaster tried to get the Infinity Stones for themselves. The seventh Infinity Stone secretly resided in the Ultraverse and took hold of Sersi.
With Angelina Jolie believed to be playing Sersi in The Eternals, there is at least the chance that she could be linked to the seventh Infinity Stone. The introduction of it would be a massive reveal for the MCU, especially since the Ego Stone is the most powerful of them all. It essentially is as powerful alone as the other six are together, and the combined power of all seven created a villain known as Nemesis. This could make the seventh stone one of the most coveted artifacts in all of the MCU, with Sersi and her fellow Eternals possibly even being the ones tasked with keeping its secret or demolishing it.
The power of the Ego Stone could make it even more desirable than the past stones, which would give The Eternals some high stakes if it included the stone. The movie potentially being set in the distant past of the MCU would also allow The Eternals to introduce the Ego Stone centuries ago and even dispose of it before the Avengers, Thanos, or any other characters could get their hands on it.
Even if Marvel Studios wanted to use the Ego Stone in the MCU, the complication with doing so could come with its origin and connection to Malibu Comics and the Ultraverse. Marvel Comics has yet to reuse the stone since the initial 1995 crossover story and has elected to focus on the original six stones instead. This would make it an even more surprising addition to the MCU, but would also give Marvel Studios incredible freedom in adapting it. While there are no rumors that it will appear in The Eternals, the movie is the best possible place for such a revelation to come.