Astral Dimension

"What did you just do to me?" "I pushed your astral form out of your physical form."

- Stephen Strange and the Ancient One

The Astral Dimension is a parallel dimension where the soul exists outside of the body.

Meeting the Ancient One
During Stephen Strange's first encounter with the Ancient One, he initially rejected the idea of souls and multiple universes along with all the other non-scientifically proven statements she made. To shut him up, the Ancient One pushed Strange's astral form out from his physical form, effectively forcing Strange briefly into the Astral Dimension.

Strange's Training
Upon starting his training in the Mystical Arts, Strange quickly became interested in the use of Astral Projections, despite Wong warning that he was not ready for it. Strange quickly became skilled in entering the Astral Dimension and frequently did so to keep studying while his physical body was sleeping.

Hospital Incident
When Stephen Strange was injured as a result of his conflict at the New York Sanctum, he stumbled through a portal into the Metro-General Hospital. There, Strange left his physical form by simultaneously assuming the astral form and entering the Astral Dimension, rendering his body unconscious. During this time, he helped Christine Palmer perform surgery on him by re-emerging in the regular universe in his astral form. Palmer was shocked by this stunt and assumed Strange was dead at first. However he was followed by the astral form of Lucian, one of the enemies he had just overcame. They battled it out in the Astral Dimension, and some of their actions had weak and muffled effects on the regular dimension. While they fought, Palmer continued her attempts to resuscitate Strange, using duel defibrillators. As it happened, this fact was able to energize Strange's astral form. Strange realized he could use that power against Lucian while in the Astral Dimension, so he asked Palmer to keep using the defibrillator. Strange forced the power through Lucian's astral form, completely incinerating him in the process.

Death in the Astral Dimension
Having been rushed to a hospital, the Ancient One left her physical body and entered the Astral Dimension, with Stephen Strange quickly following her. In her dying moments, the Ancient One witnessed lightning strike New York alongside Strange. They stretched her dying moments into minutes in the Astral Dimension together. Her physical body then died, and her astral form faded at the same time.