Extreme Isolation is an area of Arkham Asylum located within the Intensive Treatment Center. It is reserved for only the most dangerous of inmates and is considered to be the most secure area on Arkham Island. Notably it is the only part of Arkham that Batman is unable to get into during the game.
Arkham Asylum Incident
At some point, Dr. Penelope Young, after creating the Titan Henchman, banished the monster to Extreme Isolation out of fear. Later the Titan Henchman was released by the Joker whom had lured Batman into the room leading to the entrance of Extreme Isolation.
After a battle in which Batman got thrown around the room, the Titan Henchman unexpectedly died of a heart attack. The Joker disappointed by this development but enthusiastic that he could fix the flaw, offered to let Batman kill him. When Batman predictably refused, the Joker escaped into Extreme Isolation while Batman was unable to follow.
After this Extreme Isolation was never mentioned again in the game.
Arkham Knight Incident
Near the end of Batman: Arkham Knight, when the Joker infection is rapidly beginning to take over the Batman's mind, Batman is able to turn the tables on his arch-nemesis and trap him in what appears to be one of the cages that leads to the Extreme Isolation area.
With one last goodbye to his hated enemy Batman finally defeats the Joker and traps him forever.
- Extreme Isolation is the only area of Arkham Island that is never seen as Batman is unable to enter.
- This also marks the occasion of one of the few times Batman is unable to break into a place in the Arkhamverse.
- Whilst never confirmed it was implied that The Joker and The Scarecrow were kept in Extreme Isolation.