Originally from Islamabad, Mahreen was a doctor and was certified in London, but when she arrived in Gotham her medical degree didn't transfer. Despite her training, she chose to take a job as an orderly at Arkham Asylum. She worked alongside Eric Border, and was once attacked by Joker's Daughter.
Mahreen was later kidnapped by a group of five inmates, who turned on her when she insisted the Joker was not the savior they believed he was. Barricading herself in a room, she encountered Border, who revealed his true identity as the Joker. The Joker gave her a revolver with six bullets, right before the inmates burst through the door. Firing all six bullets, it is unknown if Mahreen was killed by the inmates or shot herself.
- Journalism: Dr. Zaheer spent months writing a tell-all book about what she thought was the Joker's true origin. However, she later found out that all of her facts were forged and orchestrated by the Joker himself, who tricked Zaheer into writing a book that is most likely untrue. 
- 9 Appearances of Mahreen Zaheer (Prime Earth)
- 2 Images featuring Mahreen Zaheer (Prime Earth)
- Quotations by or about Mahreen Zaheer (Prime Earth)
- Character Gallery: Mahreen Zaheer (Prime Earth)