Blind and connected to Satellite Five feeds at the age of five by dozens of cables, the Controller acted as the eyes and ears of the Daleks. Aided by programmers, she constantly monitored the transmissions that flowed through her. (DW: Bad Wolf) Essentially, she served a function similar to the Editor's for the Jagrafess a century before, who also had occupied Floor 500 of the satellite, though the Controller had less say over her actions. (DW: The Long Game)
Nevertheless, the Controller loathed and plotted against the Daleks, ensuring that the Doctor and his companions would appear in game shows on Satellite Five (now called the Game Station), which the Daleks ignored. She waited until a rare solar flare temporarily disrupted communications between the Dalek fleet and her.
The Daleks could not monitor her thoughts, letting her warn the Ninth Doctor of the enemy "waiting in the dark" and pass on to him the co-ordinates of Rose Tyler, which would enable him to rescue her, though she did not at that point reveal to the Doctor and his allies the identity of her "masters".
The Controller told him part of the coordinates (5.6.1.434. sigma 777) before she was transmatted to the main Dalek saucer, where the Daleks quickly exterminated her. (DW: Bad Wolf)
When Davros made the comment How many more have died in your name to the Doctor, the Controller appeared in a flashback of people that the Doctor was unable to save. (DW: Journey's End)
- The Daleks also employed a Controller as their collaborator on an alternative Earth which they had conquered. (DW: Day of the Daleks)