When Doctor Strange went into the Dark Dimension to save Spider-Man, Dormammu used his power to seal the portal back to Earth which trapped Doctor Strange and Spider-Man in the Dark Dimension. However, Doctor Strange used the Twelve moons of Munnopor to open the sealed portal and return to Earth.
In the comics
Munnopor's origins are unrevealed. It is one of the Principalities, god-like and/or demonic beings invoked for mystic power.
Munnopor is a living planet in an alternate dimension that can take human form which is usually that of a blue skinned woman. The surface of Munnopor is covered with a mist and twelve moons orbit the planet.
As many other powerful mystic beings, Munnopor was involved in the War of the Seven Spheres, a Pan-cyclic conflict between magic entities which will endure for 5000 years.
Munnopor, looking for a champion to fight for her in the War of the Seven Spheres, thought she had the right to enslave Doctor Strange, because of the many times she granted her help to the sorcerer to cast his spells. So, she reached the dimension where Doctor Strange was. There, she found that many other mystic entities sought for the sorcerer's service: the Vishanti, Cyttorak, Watoomb, Ikonn, the Seraphim, the Faltine, Raggadorr, Santannish, Valtorr and Denak. Unable to fulfill none of the request, Strange pronounced the Enchantment of Emancipation, refusing to serve Munnopor and any other being in their multi-dimensional war. Munnopor and the other mystic entities then, had to accept Strange's denial of service, so they hurled him back to Earth but negated him any help in the future.
- Doctor Strange (Mentioned only)