Army of Meanwhiles and Neverweres

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

The army could have been like their king and possibly paradoxes or creatures who never existed but were kept in some form of life, presumably by the Could've Been King and this is why they served him.

The Eleventh Doctor also referred to the stone-like echoes of the Daleks and Cybermen scattered around the Pandorica after the Total Event Collapse as "Footprints of the Neverwere." (DW: The Big Bang)