Astral projection

Astral Projection was a process wherein the consciousness of being who's in a state of slumber or comatose, left their body, into an "astral body" where they could travel into the real world or in different planes of existence, throughout time and space.

Instances

 * In Sunnydale 1997, Billy Palmer manifested as an astral body after he was beaten into a coma. Along with his consciousness, the nightmares of the people of Sunnydale manifested in reality.
 * In Los Angeles 2003, after dosing herself and Angelus with the mystical drug known as orpheus, Faith Lehane and the said vampire entered a mystical walk in Angel's mind, witnessing past events in his life. During these trials, they were unable to interact  with any of the scenery and this period took a close when Angelus began to fight Angel, cumulating to the point Angel's soul was restored.
 * A year later, the comatose Cordelia Chase became an astral body and used her last day on earth to assist Angel and his team in preventing Wolfram &amp; Hart's failsafe being released by Lindsey McDonald. This time, Cordelia's astral body could interact with the world but confirmed dead after her time was up.

Appearances

 * "Nightmares"
 * "Orpheus"
 * "You're Welcome"