Simon Stagg is one of the richest industrialists in Gotham City and owner of Stagg Industries.
In "Hunted", Simon Stagg was kidnapped and tormented by Professor Pyg and Mister Toad because, as an industrialist, along with Michael Holt and Bruce Wayne, built over some land killing the animals that lived there. He was eventually from Pyg with the help of Alfred Pennyworth and Batman, despite Stagg's reluctance to help Alfred even though he saved his life.
In "Toxic", Rex Mason wanted to marry Stagg's daughter, Sapphire. On the surface Simon pretended to be happy for them but in reality he was furious and tricked Mason into getting trapped in Project Metamorpho and gassed him, mutating Rex into Metamorpho.