What is the name of the alternate dimension ruled by Dormammu?

The alternate dimension ruled by Dormammu is the Dark Dimension. In the Marvel Cinematic Universe, Dormammu is a powerful interdimensional entity who seeks to absorb other worlds into his domain and transform their inhabitants into Mindless Ones.

The Dark Dimension is central to Doctor Strange (2016). Kaecilius and his followers believe Dormammu can grant them eternal life, but their bargain would bring Earth under his control. Doctor Strange ultimately uses the Time Stone to trap himself and Dormammu in a repeating time loop.

The Dark Dimension is sometimes confused with the Mirror Dimension or the Quantum Realm. The Mirror Dimension is a magical training and combat space used by sorcerers, while the Quantum Realm is a subatomic realm associated with Ant-Man and the Wasp. In Marvel Comics, Dormammu has ruled the Dark Dimension since his early appearances in Strange Tales, beginning in 1964.