Serena

Lady Serenadellatrovella (Serena for short) was a Time Lady assigned to help the Second Doctor by the Celestial Intervention Agency.

Following the Doctor's trial (TV: The War Games) on Gallifrey, the CIA had him perform tasks for them, offering to amend his original sentence of execution in favour of exile if he would act as a deniable agent in matters they would prefer not to be seen getting publically involved in. The CIA intended for Serena to help the Doctor prevent the Players from interfering with the history of Earth.

Serena sacrificed herself to save the Duke of Wellington. The Player called Valmont attempted to to shoot the Duke at a ball the night before the Battle of Waterloo. Serena intercepted the shot, but the musket ball tore through both of her hearts and killed her instantly, which made regeneration impossible. (PROSE: World Game)