Mad Hatter's Fear Gas- Arkhamverse (Batman Arkham Unhinged)

First Appeared: Batman: Arkham Unhinged (2011)

At some point the Mad Hatter obtained a sample of the Scarecrow's fear gas, which he modified with other chemicals to make his own variant of the drug.

After Batman infiltrates the Mad Hatter's Hat Shop and defeats the Wonderland Gang on his mission to free Vicki Vale from Hatter's tea party, Hatter uses the gas to infect Batman. The gas causes him to see Poison Ivy, Catwoman and the Carpenter as Lewis Carrol styled characters.

Batman injects himself after the fight with the “Jabberwocky,” so that the gas won't completely take him over. He keeps a syringe full of an agent that brakes down the toxin in his utility belt, making sure before he did use the agent that his adrenaline levels subside.

Cheshire- Arkhamverse (Batman Arkham Origins)

First Appearance: Batman Arkham Origins (2013)

Cheshire is an assassin, who was contemplated to take part in “Black Mask”'s one night deal to kill the Batman on Christmas Eve.

“Black Mask” had a file on her along with several other assassins, but decided that the eight assassins he had hired were either the most qualified or suitable for the job, rejecting her.

Batman discovers her file in the Sionis Steel Mill office along with David Cain and Black Spider.

Protocol 11- Arkhamverse (Batman Arkham City)

 First Appearance: Batman Arkham City (2011)

Protocol 11 is a a fail safe that Hugo Strange built into Wonder Tower in the case of the tower being compromised and his plans failing. On the night of Protocol 10, Hugo Strange uses his last breath to trigger the explosive in the tower and kill both Batman and Ra's in the blast.

After Batman compromises Wonder Tower and Oracle shuts down Protocol 10, Ra's al Ghul arrives and stabs Hugo Strange through the chest. He tries to plead with Ra's that he just needs more time to defeat Batman, but Ra's tells him that he failed to see his “vision” through. Ra's turns away from both Batman and a dying Strange to bask in the destruction. Batman snarls that he will stop him, but Ra's merely laughs and says that he doubts it. In his last breath he remotely commands the tower with voice activation to activate Protocol 11, using the password “Wayne.”

Oracle warns Batman to get out of the tower and grabbing Ra's, dives from the tower as a five second countdown begins and the whole tower explodes.

David Cain- Arkhamverse (Batman Arkham Origins)

First Appearance: Batman Arkham Origins (2013)

David Cain is an assassin who has connections with Shiva.

He was considered by Joker to take part in the one night only challenge to kill the Batman on Christmas Eve, however was rejected along with Cheshire and Black Spider.

Batman finds his file along with Cheshire and Spider in the office of the Sionis Steel Mill.

Black Spider- Arkhamverse (Batman Arkham Origins)

First Appeared: Batman: Assault on Arkham (2014)

Eric Needham is a famous and dangerous assassin for hire.

Joker considered hiring him to kill Batman on Christmas Eve along with the other eight assassins, however decided against it and rejected him along with David Cain and Cheshire.

Joker had a file on Spider, which he left in the Sionis Steel Mill office with the other rejected assassin's files.