Dark Places of the Inside
From Tardis Wiki, the free Doctor Who reference
The Dark Places of the Inside was the name for the dimension to which the Federator banished the Mara from Manussa, thereby ending the evil of the Sumaran Empire. (TV: Snakedance)
Tegan entered this place after falling asleep beneath some wind chimes on Deva Loka. It was complete darkness, save for a metal structure of some kind, and seemed to be affected by a person's thoughts. The/Several Mara manifested itself/themselves as Anatta, Anicca, and Dukkha, the former two believing Tegan to not be real, while the latter tempted her into letting him have her body for a while. (TV: Kinda)
- The metaphysical nature of the Dark Places of the Inside mean that they may exist in everyone's minds, as it is unclear if Tegan was just in her mind or another reality altogether.