Mr. Freeze

Once a respected and brilliant scientist, Dr. Victor Fries turned to a life of crime after his wife, Nora Fries, who Victor cryogenically froze to develop enough time to create a cure for her rare illness, was stolen away from him by his corrupt CEO, Ferris Boyle. In the confusion, Fries was drenched in the cryogenic chemicals that he had created to freeze Nora, which changed his metabolism. The result was Mr. Freeze, a cold blooded villain motivated by the desire to save and cure his wife and kill anyone who would stand in his way.

After Arkham
Dr. Victor Fries was negotiated into entering the prison by Hugo Strange under the promises of being incarcerated with his wife, Nora, and the tools he needed to cure her. But after discovering Strange double-crossed him and had given Nora to Joker as blackmail to create a cure for his Titan blood poisoning, Freeze stormed Wonder Tower, only to be captured by TYGER guards. There, Strange handed Victor over to Penguin as apart of their deal, and became a trophy of Cobblepot's in his museum.

Batman: Arkham City
While searching for Mr. Freeze, Batman was attacked by the Penguin who was using Freeze's cryogenic weapons for his own amusement. Batman found Freeze locked in a display case under a heat lamp, weakened but alive. Batman and Freeze exchanged words, and after some "persuasion" Freeze divulged the weak points of his weaponry. Batman recovered an inhibitor chip from Freeze's suit and managed to disable the weapon. After battling Solomon Grundy and defeating the Penguin, Batman confronted a fully armored Mr. Freeze. Freeze informed Batman that the cure was incomplete and that the only way to complete it was to find some kind of "restorative element" to stabilize its composition. Batman told Freeze that he knew a man named Ra's Al Ghul, who had been exposed to a regenerative chemical for centuries. Freeze told Batman to bring him a sample of Ra's Al Ghul's blood in order to synthesize the cure.

After recovering a sample of Ra's Al Ghul's blood, Batman confronted Mr. Freeze in the GCPD Building. Freeze quickly produced two vials of the antidote and locked one of them away in a wall safe. Batman ordered Freeze to give him the cure, but he refused and crushed the vial. Freeze told Batman that the Joker kidnapped Nora and demanded that he bring her back to him. After Batman tried to recover the other vial, Freeze launched a full scale attack.

Batman, using his vast array of techniques and gadgets, was able to progressively break through Freeze's defenses and overpower him; punching through his protective glass dome and beating him senseless. As Batman was punching Freeze, he began to have hallucinations of the Joker laughing at him. Realizing that he's wasted enough time Batman attempted to retrieve the second vial of antidote. When he opened the safe however, Batman discovered that Harley was able to break into the safe and has stolen the only remaining sample. Batman lamented that getting into the Steel Mill will be extremely difficult due to the Joker's security. Mr. Freeze, accepting his role in Batman's predicament, offered him cryogenic projectiles to make his venture more manageable. Batman promised Victor that he will find Nora before leaving.

It can be assumed that after the events of Arkham City Freeze was returned to the temporary holding cells for former Arkham Asylum patients while the island was refurbished for opening.