Illegal Operations - Batman: Arkham City (2011)

While in residence at Arkham Asylum, Hugo Strange experimented on prisoners as part of the process leading to him unlocking the workings of the mind in order to control it. In order to cover up his experiments, he arranged for these poor individuals to be lobotomized, locked in the cells and forgotten.

It was during these experiments that Strange perfected his ability to place posthypnotic suggestions in the minds of his victims; a technique he used to guarantee absolute loyalty from his handpicked TYGER guards.

After escaping from custody, the Joker released the lunatics and allowed them to roam free across Arkham Island in an attempt to stop Batman.