Nightmare Child

Davros' ship flew into the "jaws" of the Nightmare Child during the first year of the Last Great Time War, supposedly destroying him and his ship in the process. This event happened at the Gate of Elysium.

Dalek Caan, who had escaped from 1930 using an emergency temporal shift (DW: Evolution of the Daleks), arrived in the Time War (despite it being Time-locked) and flew into the jaws of the Nightmare Child to save Davros from destruction. (DW: The Stolen Earth)

 it has not yet been stated what precisly this is many belive it is an organism or it could be a black hole and various othe theories exhist but so far it has only been mentioned once