The Skaro Degradations are first mentioned in the Doctor Who television serial "The End of Time" (2009), where the Tenth Doctor says they were one of the horrors of The Last Great Time War. They later appear in the War Doctor novel "Engines of War" (2014) by George Mann, described as being unstable and unpredictable abominations created by Dalek experiments to retro-evolve their own genome. Three types are mentioned in the book. Glider Degradations travel by hovering above the ground. The Dalek mutant is housed in a clear, reinforced compartment set beneath a standard Dalek dome and resembles a limbless, humanoid torso. Mechanical arms and energy weapons are located on both sides of the casing. Spider Degradations are egg-shaped with red and black hemispheres, move on three legs and are armed with four energy weapons. Temporal Weapon Degradations are similar to Special Weapons Daleks and equipped with a temporal cannon capable of erasing its victims from history.