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.

Black Mask (Joker)- Arkhamverse (Batman Arkham Origins)

First Appearance: Batman Arkham Asylum (2009) (Joker)
Batman Arkham City (2011) (Black Mask)

When the Joker first came to Gotham around the Christmas Eve period, he decided to capture and impersonate Black Mask, who had made himself one of the top villains of the city, as he saw that he had plenty of resources and connections. 

After Joker had kidnapped Sionis from his safe house and killed his girlfriend (Tiffany Amborse), he held him hostage in his own Steel Mill, where he tortures him to find out every little detail that he could use to convince Gotham he is Black Mask. Finally after several days, he fully takes up the mantle of Black Mask, now with his power and henchmen at his disposal.

He hired eight assassins to perform a hit on Batman for a one night deal of $50 million. However a slight catch to that, was he kept the presence of the other assassins a secret from each other. 

He hires Deathstroke to set up a trap, involving an exploding warehouse and a briefcase to lure out the Batman. This plan to kill him only failed due to the fact that Deadshot intervened, trying to collect the bounty himself.  Deathstroke confronts him about hiring other assassins, but "Black Mask" ignores this, telling him that although he missed his chance to kill Batman, the night is still young. He then proceeds to beat an injured henchmen to death for no real reason.

"Black Mask" gives the order for his henchmen to bring him Martin Joseph, the warden of Blackgate. When Joesph is brought in front of him, he tortures the later. Along with threatening his whole family, Joker burns out his eye with a lit cigarette, until he agrees to lower the security in the prison.

On Christmas Eve, after the arrival of the assassins and the alterations to Blackgate's security, Joker takes Killer Croc with him to brake into the prison. After murdering many guards and destroying part of the prison, he takes Gillian Loeb (G.C.P.D Commissioner) hostage. He contemplates killing both Loeb and Calendar Man (who is about to be executed), but due to it being Christmas, he thought it would be interesting to see what Day would do. He tells Loeb that he is starting with a new "slate" and that he wasn't on it. He watches Loeb die, before taking his men to the roof to escape in helicopters. However before they leave, he orders Croc to grab the memory card of Penguin's drone that is spying on them.  He berates Croc, threatening to smash his face if the card survived being destroyed by the latter.

Upon leaving Croc to deal with Batman, he strikes a deal with S.W.A.T leader Branden so he can also collect the bounty on Batman's head. He also hires Edward Nigma to put up jamming signals in G.C.R Towers, paying him with the capital that would go onto fund for Enigma's data handlers to be bribed and bought.

While Batman is trying to hack into the National Criminal Database beneath the G.C.P.D headquarters, Black Mask orders his men to plant bombs beneath many Gotham services and buildings: ranging from fire department, sewer pump stations, subway station and the police headquarters itself. 

He goes to the bank in an ambulance, where he kills many of the employees of the bank, tortures some with Christmas decorations and takes the bank manager hostage. Before Batman arrives, he uses Joker Toxin to poison her. 

When Batman does come, he pretends to not know what Batman is talking about. However he gives up and beats Sionis in a rage when Sionis (who he had brought with him to get into the bank, to bypass the biometric control systems) threatens to kill him.He finally reveals himself to Batman, revealing that he was the one who hired the assassins and was running the operation.

Joker sends his men away to kill and rob, while he went to the Gotham Royal Hotel. He hired Branden to keep Batman/ Gordon and the media away from the hotel, before meeting with his assassins in the Penthouse. There he reveals his true identity to the assassins present.

DeSaad (Young Justice Invasion)

First Appearance: Young Justice (2010): Season 1 Episode 17 Disordered

DeSaad is a New God who hails from the planet Apokolips. He is Darkseid's chief torturer and scientist, also acting as the link between Earth and Apokolips when transporting weapons to Intergang.

On July the 5th 2016, DeSaad was present on the surface of  Apokolips when Vandal Savage arrived via a Boom Tube. He watched in silence as Savage and Darkseid shake hands and begin their business.