Of all the Infinity Stones in the Marvel Cinematic Universe, the Time Stone might be the most useful. While it lacks the sheer strength of the Power Stone and the manipulative abilities of the Mind Stone, it has proven invaluable when in the right hands. But it also possesses the ability to ruin an otherwise perfect plan if used incorrectly, a constant fear Doctor Strange saw drilled into him in his solo film.
That's why a new fan theory about how the Time Stone could have backfired against Thanos is so intriguing. It would explain some of the time travel elements that have been all but confirmed to exist in Avengers: Endgame, and might prove to be the accidental ace in the hole that the heroes need to save the day and reverse the effects of the infamous snap.
Time Is A Fickle Thing
The Time Stone first came to prominence in Doctor Strange. Revealed to be the source of power for the Eye of Agamotto, it gives the user control over time itself. However, the sorcerers of Earth were careful not to abuse that power out of fear of creating uncontrollable time loops; they were aware of the potential consequences of such actions, and were rightfully concerned about them. As Mordo and Wong explained to Stephen Strange after he's begun toying with the stone, "Temporal manipulation can create branches in time. Unstable dimensional openings. Spacial paradoxes... time loops!"
Their warning of the Eye's wielder being stuck reliving the same moment forever and forever ends up informing Strange's eventual trick to stop Dormammu from breaking through to their reality. And while Strange managed to use this trick to defeat his enemy, the dangers his fellow sorcerers warned of are still very present for someone who isn't a master of the mystic arts. If you don't know what you're doing, using the Time Stone can be a very dangerous act, which is why it matters that Thanos uses the stone right after claiming it.