The Count was the name assumed by a Player whilst on Earth.
He tried helping Napoleon Bonaparte to win the Napoleonic Wars, but have the Empire collapse and cause more internecine conflicts, thus creating the potential for more games. Also, he and the Countess attempted to kidnap Winston Churchill and deliver him to Germany. Both plans were stopped by the Second Doctor. (PROSE: World Game)
The Count and Countess sent an assassin to kill Churchill during the Boer Wars, but were stopped by the Sixth Doctor. In a later struggle, the Countess accidentally shot and killed the Count. She was not mad at the Doctor, but invited him to join the Players' Game, since he manipulated history like them. The Doctor denied what he did was the same thing, so the Countess left with the Count's body. (PROSE: Players)