From Destinypedia, the Destiny wiki
The Dreaming are a group of entities known to the Awoken. They are said to be in a sort of symbiotic relationship with the Awoken, the two species driving each other's will, and the Dreaming City has been named after them. Shuro Chi remarks they have been known to manifest as faces carved in rock and could be the ones who formed the mysterious statue in the Spine of Keres.
List of appearances