Horde of Travesties

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

These could have been timelords, daleks, or another race involved in the time war as their name implies they are a group of absurd/distorted beings, possibly because of damage from the time war. They could have been the Gelth as they were damaged from the war and they were a distorted version of their former selves.