John Deegan became a doctor at Arkham Asylum.
To find Deegan, Kara Danvers, Caitlin Snow, Oliver Queen, John Diggle, Barry Allen, and Cisco Ramon snuck their way inside the asylum. After Oliver and Diggle found Deegan in his office and attempted to convince him to revert reality to its original state, the doctor opened all the cell doors of the asylum to create a distraction, setting the prisoners free. With the help of Batwoman, the seven managed to bring the prisoners back to their cells and obtain the Book of Destiny from Deegan.
At some point, Batwoman lodged a live audio-recording batarang in a ceiling inside the asylum to eavesdrop on the prisoners.
After Deegan's psyche was distorted by the excess energy from the Book of Destiny, he was relieved from his duties as a doctor and was admitted as a new patient in Arkham.
- John Deegan (doctor; became a patient)
- O. Cobblepot
- J. Crane
- John Deegan (former doctor)
- Tommy Elliot
- Victor Fries
- M. Guggenheim
- Roger Hayden/Psycho Pirate
- P. Isley
- B. Karlo
- S. Kyle
- E. Nigma
Behind the scenes
- In the DC comics, Arkham Asylum is where those of Batman's foes considered to be legally insane are incarcerated.
- Bane's mask from The Dark Knight Rises can be seen along with Victor Fries's cold gun, so it can be assumed that both Bane and Fries were or are still both inmates of Arkham for some time.