Nightmare Child

Nightmare Child was an unknown event or thing, that the Time War ran into during the first year of battle. Davros' command ship flew into the "jaws" of the Child and was apparently killed, though The Doctor did attempt to save him. Despite the war being Time locked, Dalek Caan later managed to arrive in the middle of the battle via an emergency temporal shift, (DW: Evolution of the Daleks) and saved Davros from the "jaws" of the Nightmare Child (DW: The Stolen Earth)

It has not yet been precisely explained what a/the "Nightmare Child" actually was.