Garfield Lynns, professionally known by the alias of Firefly, is a super-villain who appears in DC Comics that are centered around superhero Batman. He is a pyromaniac who originally began as a criminal before carrying out arson attacks in Gotham City.
The version of Firefly that appears in Ready Player One is the version that appears in the game Batman: Arkham Knight.
Firefly was originally a petty criminal named Garfield Lynns, known for his daring moves, but since he was cunning with using fire-related strategies, he soon carried out arson attacks on buildings around Gotham City. After making an actual suit based on Fireflies, he decided to be a criminal and wreak havoc on Gotham.
Role in Ready Player One
He is seen in the final battle, once Parzival lifts up the boombox and plays We're Not Gonna Take It by Twisted Sister, and is seen on his right side.