The Bank of Karabraxos was a financial institution used by the ultra-wealthy of the galaxy. It was the most secure bank in the galaxy: no one stepped foot on the planet without protocols, all movement was monitored, air consumption was regulated and DNA was required at every stage. Therefore, extremely valuable items were stored in the bank as well.
The bank made use of the Teller, a creature that could detect guilt. If there was an intruder, the Teller would scan the suspect's mind for criminal intent and if found, it would liquefy their brain. According to Head of Bank Security Ms Delphox, the person's next of kin would be informed and incarcerated; an extreme measure to ensure that the plan the victim had could not be carried on, regardless if their family was innocent.
At the behest of a future Madame Karabraxos, the Twelfth Doctor, Clara, Saibra and Psi broke into the bank to free the Teller and his mate. Shortly after, the bank was destroyed in a solar storm. (TV: Time Heist)