Simon Stagg founded Stagg Enterprises with his friend Dr. Alex Sartorius. Stagg eventually decided to sell their pharmaceuticals as bioweapons and perform unethical experiments, causing his former friend Dr. Sartorius to try and expose Stagg. Unfortunately, Stagg used Alex as a lab rat for his experiments with Scarecrow's Fear Toxin. He then made a deal with Scarecrow, hoping to use his fear gas for profit. He created a weapon known as the Cloudburst, which launches and amplifies the effects of the fear toxin. Stagg even supplied his Nimbus Tech to the Arkham Knight's militia, but he then discovered that Scarecrow wasn't interested in the profit that the fear toxin could bring them, instead intending to use it and the Cloudburst in his revenge scheme against Batman and Gotham City. He tried to double-cross Scarecrow, which made Crane attempt to punish him.
After being rescued by Batman, Stagg lied about the Cloudburst's functions. However, Stagg ended up captured by Scarecrow's men again, as Batman was temporarily incapacitated due to a hallucination caused by the Joker's blood. Stagg was then placed in a cell with fear toxin being leaked inside as a form of execution by Scarecrow. He was rescued by Batman once again, though he had learned of the Cloudburst's real purpose, and knocked Stagg out.
He then activated several security measures to ensure neither the Arkham Knight's forces nor Batman could reach him. However, Batman did manage to reach him and he explained how to bypass the Cloudburst's abilities with Nimbus Tech. Batman then trapped him in a cage. He was later taken in by the GCPD and placed in a holding cell. 
- This version of the character is exclusive to the continuity of the video game Batman: Arkham Knight and is an adaptation of Simon Stagg. The original character was created by Bob Haney and Ramona Fradon and first appeared in The Brave and the Bold #57.
- 3 Appearances of Simon Stagg (Arkhamverse)
- 1 Images featuring Simon Stagg (Arkhamverse)
- Quotations by or about Simon Stagg (Arkhamverse)
- Character Gallery: Simon Stagg (Arkhamverse)