Doctor Strange saved Earth from being consumed by the Dark Dimension when he made a deal with Dormammu, but for that, he had to be killed over and over again, which was possible by trapping themselves in a time loop – so, how long was Doctor Strange in the Dark Dimension with Dormammu? The Marvel Cinematic Universe began to explore other realms with Thor, different planets with Guardians of the Galaxy, and mysterious dimensions with Doctor Strange, expanding this universe of connected movies and making way for the multiverse, which will play a big role in the MCU’s future.
Doctor Strange gave the audience a glimpse at some of the dimensions within the multiverse in the sequence where the Ancient One (Tilda Swinton) sent Stephen Strange (Benedict Cumberbatch) through the multiverse, showing places like the Mandelibus Dimension and the Dark Dimension. The latter was revisited in the final act of the movie, where Kaecilius (Mads Mikkelsen) and the Zealots succeeded in bringing the Dark Dimension and Dormammu to Earth, killing Wong (Benedict Wong) in the process. Strange then used the Eye of Agamotto to reverse time and bring Wong back, and as he, Baron Mordo (Chiwetel Ejiofor), and Wong prepared to fight, they were interrupted mid-spell, resulting in time being frozen. Kaecilius declared that Dormammu’s arrival couldn’t be stopped and that the Dark Dimension is beyond time, which gave Strange an idea on how to defeat him.
Strange headed to the Dark Dimension and took time with him, a concept Dormammu was not familiar with. Strange requested a bargain, and after defending himself, Dormammu killed the sorcerer, who then reappeared and repeated the same words as before. Confused, Dormammu asked if it was an illusion, with Strange explaining that he “brought a little power” from his world, and that power was time. Strange created a loop that trapped him and Dormammu, thus allowing him to be killed by this evil entity over and over again and come back every time. Strange was killed in many different ways, with Dormammu telling him he was going to spend eternity dying in agony, but Strange assured him it was a price worth paying to protect Earth, and that also made him his slave. Dormammu eventually gave up and made a deal with Strange, who then returned to Earth.
As time froze on Earth, when Strange returned only a couple of minutes seemed to have passed, but he spent a lot more time in the Dark Dimension. In 2018, Doctor Strange screenwriter Robert C. Cargill explained that Strange spent a lot of time in the Dark Dimension, but that was something they left “intentionally vague with room to address it later”. Cargill confirmed that, while on Earth only a few minutes passed, Strange wasn’t in the other dimension “just a few minutes”, and it was long enough to “gain even more mastery over his powers”. This explains why he was a lot more skilled in Thor: Ragnarok, even though not much time passed between these movies. If Strange was in the Dark Dimension long enough to master his powers, experiment, and learn new tricks, the safest bet is to assume he was there for years.
Director Scott Derrickson told Empire back in 2016 that there was originally a line in that scene where Strange said they had been “through this a thousand times”, which would have been a good hint at how long he was trapped in the loop. Of course, as time doesn’t exist in the Dark Dimension and time was frozen on Earth when Strange left, it’s tricky to calculate exactly how long Doctor Strange was in the Dark Dimension, but there’s the possibility of this being addressed in Doctor Strange in the Multiverse of Madness – what’s for sure, however, is that he spent at least a couple of years there.