WARNING: The following contains spoilers for What If...? Season 1, Episode 9, "What If... The Watcher Broke His Oath?," streaming now on Disney+.
The Infinity Stones' importance only ever seemed to grow throughout the Marvel Cinematic Universe. By the time of Infinity War, they were established as a threat to the entire universe when Thanos used them to wipe out half of all life in existence, but the scale of the MCU was not done growing. There were other universes, and at first, the Stones had clear limits.
But What If...? seems to shatter those limits, with the season finale proving that their power truly is infinite. This creates some baffling inconsistencies in the lore of the MCU's Infinity Stones and questions that will eventually need answers.
The first real limit established with the Infinity Stones involved the power of their wielder. Established in Guardians of the Galaxy as too powerful for most mortals to use, that limitation became even more explicit in Endgame when the power of performing and undoing the Snap nearly killed Thanos and the Hulk. Even more severe limitations came in Loki, where mundane Time Variance Authority employees explained the Stones become nigh-useless paperweights outside their own universe.
And yet, What If...? seems to do away with those limitations altogether as the evil Ultron takes their power for himself and uses them to threaten the entire multiverse. His power grows throughout the cosmos of his world, conquering one world after the next until his consciousness ascends to such a level, he is aware of the Watcher observing him from a place outside reality. In flagrant conflict with the limitation outlined in Loki, Ultron then uses the Stones to shatter through one reality after the next in combat with Uatu.
The contradiction upsets a manageable status quo that Loki established and creates problems in the What If...? finale none of the characters address. First and foremost: If the Infinity Stones are so powerful and there are infinite varieties of them throughout the multiverse, then how is their assembly in an Ultron-like entity not a constantly recurring threat? There is not even a straightforward explanation for why Ultron uses the stones so much more powerfully than Thanos or anyone else ever did. And perhaps most head-scratchingly, none of the Guardians of the Multiverse consider gathering Stones of their own.
It's even established in the final fight that a Time Stone from a different reality can cancel the effects of Ultron's own Time Stone. Rather than engaging him in a straightforward battle, it would make far more sense to assemble a few Infinity Gauntlets of their own to overpower the multiversal threat. When Loki introduced infinite timelines, it was wise to close off the infinite possibilities of Infinity Stones, but it seems What If...? threw Pandora's box right open.
Even if the explanation is supposed to be that the Infinity Stones were specifically powerless in the realm of the TVA, that explanation would be unsatisfactory. It seems they worked fine in the Watcher's realm, also reasonably a domain outside reality. If that truly was the solution, then the same problem will persist in perpetuity: Why is the assembly of an Infinity Gauntlet somewhere in the multiverse not a constant threat?
The MCU came so close to closing the chapter on the Infinity Saga, where the Stones constantly dominated the plot. We may be entering a new era that repeats that same cycle all over again, and if the MCU wants to stay fresh, it will do well to stave off that possibility before it spins out of control.
To figure out what's going on with the contradicting Infinity Stones, Episode 9 of What If...? is now on Disney +.