Psi Psi was an augmented human who worked as a hacker and bank robber . At one point in time , he was recruited by the Twelfth Doctor to rob the Bank of Karabraxos . Biography . In prison . Psi worked as a bank robber and efficient hacker , equipped with an augmented brain . At one point , he was arrested and sent to prison , where he was interrogated . To stop himself from betraying those closest to him , he deleted his memories of all his friends and family , a decision which he ultimately came to regret . Robbing the Bank of Karabraxos . After being released , Psi was recruited by the Doctor to help him rob the Bank of Karabraxos , the most impenetrable bank in the galaxy . Psi , along with the Doctor ' s companion , Clara , and the mutant human , Saibra , was sent down to the planet and deleted his memories of the last few hours , ensuring that he had no idea what he was doing there or why he was going to rob the bank . The group received a message from the " Architect " , who informed them of their mission and gave them no alternative . Psi and the group successfully entered the bank , using Saibra ' s shape - shifting powers to get them past the bank ' s security . In the central lobby , they witnessed the fearsome Teller , a telepathic creature kept enslaved by the bank to detect guilt in another human and turn his brain to " soup " . Psi and the gang then proceeded to go down to the lower levels of the bank . At the vault level , Psi watched as Saibra was forced to use a device they believed would kill her , as an alternative to being killed by the Teller . When the Teller was released into the lower levels , Psi tried to open the vault , but was unable to . When the Teller homed in on Clara , he attracted it towards him using his guilt , and the guilt of all hackers and bank robbers before him , before using the device on himself . Rather than killing him , however , the device merely teleported him to a ship waiting in orbit . He and Saibra returned to the bank and managed to save the Doctor and Clara from the wrath of Ms Delphox . Going down one last time to the Private Vault , Psi and the others discovered Madame Karabraxos , the director and manager of the bank , as well as the Teller ' s mate , which had been kept in a cell to ensure the Teller was completely loyal to the bank . They informed Karabraxos of the dangers an impending solar storm would do to the bank , and Karabraxos fled — though not before the Doctor handed her a piece of paper with his number on it and the message , " I ' m a time traveller " . Years later , consumed by guilt , she would use that number to ask the Doctor to break into the bank at just the right time so he could save the Teller and its mate . Psi then shared a takeaway with the rest of the gang , and was given a neophyte circuit to give him back the lost memories he so craved . He then returned to his own time and place , as did Saibra and Clara . ( TV : " Time Heist " ) Personality . Psi was a compassionate individual , placing the success of the mission over and above his own life . He was disgusted at the Doctor ' s readiness to forget the others , calling it " professional detachment . " He was brave and resourceful , using the technology augmented in his brain to help accomplish the mission . ( TV : " Time Heist " ) Abilities . Psi had the ability to store data directly into his head . He was also able to alter and delete his own memories , as well as use a device to project images on a wall . ( TV : " Time Heist " )