Skaro Degradations

The Skaro Degradations were a part of the Last Great Time War. They were described by the Tenth Doctor as one of the potential horrors that would be released when the Master broke the time-lock on the war, along with the Nightmare Child, the Horde of Travesties, and the Army of Meanwhiles and Neverweres led by the Could've Been King. (DW: The End of Time)

The name appears to reference the Dalek and Thal homeworld of Skaro, but there has been no further description of the Skaro Degradations. This leaves the actual entity unknown however the name could refer to creatures from skaro made during the war that degrade or destroy other beings.