Nightmare Child

Nightmare Child was a phenomenon or entity that was extant during the first year of the Time War. Davros' command ship flew into the "jaws" of the Child. Despite the war being Time locked, Dalek Caan managed to enter the war with an emergency temporal shift. (DW: Evolution of the Daleks) He arrived in the middle of the battle and saved Davros. (DW: The Stolen Earth). However, when talking to the TARDIS consciousness, disguised as Martha Jones, the Tenth Doctor commented he had laughed in the face of the Child.

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