Why does Doctor Supreme remain the same age for centuries in Marvel’s What If…? episode 4? Sorcerers like Stephen Strange and the Ancient One are some of the most powerful characters in the MCU, as they can perform a wide variety of spells that allow them to manipulate time, alter reality, and give near-invincible villains such as Thanos a hard time. Magic could become a source of limitless power in the MCU, but it has its downsides.
In Doctor Strange, it’s revealed the Ancient One draws energy from the Dark Dimension to retain her permanent youth. Unlike Kaecilius, she seems to be in control of her thirst for eternal life, but the dangers of the Dark Dimension still loom over her. Fortunately for the MCU’s main universe, Doctor Strange abandons his egotistical tendencies and devotes his life to protect reality, becoming wise and powerful enough to resist the temptation of eternal life and keep Dormammu’s Dark Dimension from bleeding into his universe.
What If…? episode 4 shows how easy it could have been for Doctor Strange to follow in the footsteps of Kaecilius and the Ancient One, with Christine Palmer’s death pushing him to seek a way to change the past. Strange’s determination turns into an unhealthy obsession, but instead of resorting to the Dark Dimension, he goes the extra mile and seeks hidden knowledge at the Lost Library of Cagliostro. The immense power he draws from the creatures he absorbs in order to undo Christine’s Absolute Point in time appears to make him quasi-immortal, as he only realizes that centuries have passed when he sees that his mentor O-Bengh has grown old.
Doctor Strange is ready to use the Time Stone to rejuvenate O’Bengh, but as Wong and the Ancient One warn him in Doctor Strange, the negative side effects of the Time Stone are more immediate, so even if O’Bengh agreed, it’s likely that rewinding time for him would result in tragedy. Conversely, the lifeforce that the Strange steals from the mystical creatures seems to grant him a more stable youth, but it corrupts his mind and causes his universe to collapse. As for how O-Bengh could live for so long, it’s possible that he used a less dangerous spell to achieve it, but he knows that “even in our world, death is part of the plan”. So, while it’s technically possible to achieve eternal life in the MCU, it doesn’t seem to be easy to obtain by the most powerful sorcerers.
If neither magic nor the Time Stone are the right paths for eternal youth, how can any MCU character live for centuries without aging? The closest option is to have been born with extraterrestrial genes, as the Eternals and the Asgardians have a natural lifespan of thousands of years. Another option is staying at the Time Variance Authority and the Citadel at the End of Time, where He Who Remains and his employees don’t seem to be affected by aging. However, Doctor Strange’s downfall in Marvel’s What If…? episode 4 shouldn’t be a reason to discard magic just yet, as Agatha Harkness has been able to age very slowly by stealing power from other witches since at least the Salem Witch Trials.