The Arkham Staff are the medical and security staff that work at Arkham Asylum, to help the Inmates and keep them secure and safe in the Asylum. Not the inmates themselves.
Aaron Cash is a corrections officer at Arkham and one of the few Asylum employees that Batman trusts. Cash's hand was bitten off by Killer Croc and Cash keeps a wallet made out of Croc's skin as payback.
Formerly Jeremiah Arkham's assistant who later went on the become director of the Asylum. Alyce Sinner was a cult member and wears red ribbons in her hair that represent the 7 deadly sins.
Founder of the Asylum who later went insane. Amadeus Arkham is also the uncle of Jeremiah Arkham.
Harleen Quinzel was a psychiatrist appointed to the Joker whom she fell in love with and who eventually drove her insane.
Hugo Strange is often depicted as an insane doctor at Arkham who relies on shady methods.
Jeremiah Arkham is the nephew of Amadeus Arkham and director of the Asylum. Jeremiah later become the new Black Mask.
Formerly chief of security at Arkham, Lyle Bolton later becomes the violent vigilante Lock-Up.
Quincy Sharp is the Warden of Arkham in the Batman: Arkham video-game series.
Jonathan Crane is sometimes depicted as a doctor at Arkham before he becomes the Scarecrow.