Children of Time was the name given by Dalek Caan to the group of people, consisting mostly of the Tenth Doctor's companions, who opposed their plan to destroy all of reality.
Davros believed that the Children of Time were transformed into weapons and murderers by the Tenth Doctor. Dalek Caan predicted that one of the Children of Time would "die". Eventually, this prophecy became true in a manner of speaking when the Doctor erased Donna Noble's memories of him and her time in the TARDIS. He told Wilf that "That version of Donna is dead." (TV: Journey's End)