Blanks

The Blanks were humans whose mind had been wiped of all memories and personality and were little more than puppets. (PROSE: Apollo 23)

History
The Blanks were first created on Base Diana by Professor Jackson as part of his plan to replace the minds of dangerous prisoners with those of the dying so the dying could live on. In order to do this, Jackson would erase all of their memories and personalities, effectively "blanking" them for a new mind to be downloaded into.

After the Talerian Androparg possessed Jackson, he began turning the personnel of Base Diana into Blanks with the purpose of downloading Talerian minds in instead of humans for a Talerian invasion of Earth. Some of the people he blanked did not receive Talerian minds immediately and were instead turned into effective puppets. In these cases, the original personality of the person, all of which had back-ups kept in Base Diana's data storage, would be downloaded back into the person's body so they would continue on as normal until they were needed. Once the Blanks were given a programed instruction, their personality would disappear and they would become mindless puppets that only existed to follow the instructions programed within them. Due to their mindless state, the Blanks would focus on only their task to the exclusion of all else. After completing their tasks, the Blanks original personality would return with no memory of what they did while under the control of their programing.

After the arrival of the Eleventh Doctor and Amy Pond, Amy witnessed the actions of several Blanks and was turned into one herself. Unlike the other Blanks, Amy's original personality was not restored as it was not needed for her mission to learn of the Doctor's plans to stop the Talerians and thus when she was not acting under her programing, she was mindless. Using optical stimulation from the sonic screwdriver, the Doctor was able to give Amy simple commands even while she was mindless as they retrieved her back-up. Following the Doctor's orders to keep her back-up close and safe, Amy drank it, allowing her brain to extract the imprint of her mind from the water, erasing her Blank programing and restoring the original Amy.

With the knowledge that contact with water from their back-ups would restore the Blanks to normal, the Doctor had Major Andrea Carlisle lock all of the doors of Base Diana open and rig the fire suppression system so that it could not be turned off outside of the control room she controlled. The Doctor then filled the fire suppression system's tank with water from Base Diana's reservoir and the back-ups of the Base Diana personnel before triggering the system. Contact with the water immediately erased the Blanks programing and the Talerian minds in those who had already had one uploaded. The Base Diana personnel also blanked out again for awhile, but once they regained consciousness, they had their original minds back with their Blank programing gone and no knowledge of their actions as Blanks. (PROSE: Apollo 23)