Mind Flayers were devices that were utilized by the Galactic Empire, and were later repurposed by the New Republic.
Several years after the fall of the Galactic Empire, while trapped in a cantina on the planet Nevarro by the forces of former Imperial Moff Gideon, the former Rebel Alliance shock trooper Cara Dune believed that she would be uploaded to a Mind Flayer if she surrendered. Greef Karga, agent of the Bounty Hunters' Guild, denied that Mind Flayers existed, believing them to be wartime propaganda, but Dune was not willing to find out whether he was correct.
Despite the prohibition of torture by the Galactic Concordance, the New Republic used a type of Mind Flayer, the Six-O-Two Mitigator. Doctor Penn Pershing was forced to go through a mental recalibration using lower voltages, an experimental process thought to help soothe traumatic memories to help one overcome Imperial indoctrination. However, this process was sabotaged by Elia Kane, who increased the voltage to its maximum.