From Destinypedia, the Destiny wiki
The Simulant Future is one branch of the Infinite Forest simulation in the Fields of Glass, Mercury. It is a Vex simulation of their supposed ideal far future, where they have supposedly dominated everything and neither the Light nor the Darkness are said to exist any longer. However, an unknown entity maintains a presence within the Simulant Future, which was encountered by Osiris during his time there after the death of Panoptes, Infinite Mind. The presence of this said entity may suggest a greater nature to the Future than it appears.
List of appearances