Nethersphere

Missy and the Half-Face Man in the Promised Land. (TV: Deep Breath)

The Nethersphere, also known as the Promised Land or Heaven, was an afterlife-housing realm where the recently deceased would be accounted for and sorted to certain locations it entailed. (TV: The Caretaker) Its mythical heavenly aspects were sought by many individuals hoping to attain peace, jubilation, and fulfillment.

The Half-Face Man said he was trying to reach the Promised Land. Its existence was denied by the Twelfth Doctor. When the Half-Face Man appeared to die after having been impaled upon the spire of Big Ben, he was transported to a lush garden where he encountered a woman identifying herself only as "Missy". She said that he had "made it" and that he was in "the promised land" — or, as she also called it, "paradise". (TV: Deep Breath)

Later — as from the Doctor's perspective — a soldier from the Aristotle appeared to die within the body of a Dalek and then was transported to an elegant tea room, where she, too, encountered Missy. (TV: Into the Dalek) Later still, the Doctor discovered that a ship of robots that had crashed in Nottingham of about 1190 had a programmed destination of "the promised land". (TV: Robot of Sherwood)

A policeman named Matthew in Shoreditch in Clara Oswald's home time, having been killed by a Skovox Blitzer, arrived in an area of this afterlife resembling an office, meeting a man called Seb. Seb worked for Missy, who was busy at that moment, calling this afterlife the Nethersphere. (TV: The Caretaker)

Missy is seen in a room whilst looking at Clara on an IPad, there is a Cyberman eye shaped hole on the wall behind her which is our first indication that she is in league with the Cybermen (TV:Flatline (TV story) She is also seen in this same room where she comments that she is shocked by the outcome of the solar flare crisis (TV:In the Forest of the Night (TV story)