Black Mask's Blackgate Riot

On a particularly snowy Christmas Eve, a Code 10 riot broke out at the Blackgate Penitentiary, caused by Black Mask.

Prelude
On Christmas Eve, the serial killer Julian Gregory Day, also known as Calendar Man, was to face execution for his mass murders, with Commissioner Gillian B. Loeb overseeing the execution. While meeting a press release on the event, Loeb dismissed further questions after one of the reporters implied when asking questions that it was actually Batman and not the GCPD who was actually responsible for Day's arrest.

Black Mask, however, after torturing the warden, Joseph, and threatening his family, forced the warden to make security lax to engineer a prison riot inside the penitentiary. After Black Mask and several of his men, including the hired hitman Killer Croc, broke into the prison, a dispatch was issued requesting backup as Loeb and the news crew were taken hostage. Bruce Wayne, overhearing this dispatch, donned his identity of Batman and proceeded to go to Blackgate to quell the riot.

The riot
Upon arrival, Batman deduced the entry point of Black Mask and his men due to the damaged entrance. After saving Joseph from being brutally killed by some of Black Mask's henchmen and defending himself from a panic-stricken Joseph, he then went further into the prison to locate Black Mask and the Commissioner, as Joseph had no knowledge on either's location. After defeating several of Black Mask's henchmen near the cells and interrogating them about their location, he proceeded to continue onward, including defeating several criminals near the cell that the news crew was located. During his search, he also witnessed a drone flying around the prison After blowing up a weak spot on the floor, Batman eventually located the commissioner, Croc, and Black Mask himself, the latter of whom was in the middle of a speech deploring the Commissioner for imprisoning several of his own men in the prison despite being on his payroll, and demanding that they make "big changes" to the prison. After subduing the prisoners, he then arrived at the execution chamber after witnessing Killer Croc savagely bite a prison guard. He then witnessed Black Mask release Calendar Man from the gas chamber and throw the hapless Commissioner into the gas chamber instead, under the pretense that Loeb was not part of his new plans. Batman was unable to save the Commissioner in time, but vowed that Black Mask will have a lot to answer for before defeating several of Black Mask's men who arrived to investigate. While escaping, Black Mask discovered the drone tailing him and ordered Killer Croc to destroy the drone and take the memory card. However, the crocodile-like man instead smashed it into the ground with enough force to cause a minor quake, and did not retrieve the card. An irate Black Mask then proceeded to threaten to smash Killer Croc's face if it turned out that his earlier action did not actually destroy the memory card as he claimed, which Batman overheard as he uncovered the memory card.

Upon arriving on the roof, most of Black Mask's forces escaped save for Killer Croc, due to the latter smelling Batman, as well as several of Black Mask's men on standby. After arrival, Killer Croc then fought Batman and tried to kill him. However, he ended up defeated. Batman then interrogated Croc about the whereabouts of his employer, only to learn that Black Mask hired assassins to attack Batman for a large reward. Batman then knocked Killer Croc out and dragged him back to stable ground. He was then surrounded by the GCPD led by Captain James Gordon, although he managed to escape via the Batwing.

Aftermath
Because of Loeb's murder and the revelation of eight assassins (including Killer Croc) in Gotham aiming to collect the bounty on Batman's head, the city fell into chaos during Christmas. In addition, when Black Mask, later revealed to be a new criminal mastermind known as the Joker, was incarcerated at Blackgate, another, far more destructive riot took place