The Black Mask Club was a popular lounge and hangout spot in Gotham City. Roman Sionis, also known as the Black Mask, enjoyed a steady business here, but the business was itself merely the forward-facing front of his criminal organization. He also lived in an apartment space above the club.
Dinah Lance became a performer here, quickly becoming one of the club's most popular attractions for her amazing singing voice. Black Mask also often conducted criminal affairs in the club itself, such as meeting with crime boss Mr. Keo or tying up enemies during non-operating hours.
Harley Quinn visited the club to deal with her recent break-up with the Joker, where she would first meet Lance as well as precipitate the singer's hiring as Sinois' driver by breaking his other driver's legs. Quinn, with whom Sionis had a longstanding grievance against and generally disliked, was later captured by Sionis' men and nearly killed on the club's dance floor. Quinn, however, managed to escape this fate when she offered up her services as a finder of lost things to locate the Bertinelli diamond.
After speaking to Doc, Helena Bertinelli later tracked Victor Zsasz to the club. Shortly after this, Lance witnessed Black Mask fly into a fit of sadistic rage after believing a patron was laughing at him, resulting in his humiliation of her. After seeing this incident, Lance ultimately turned against him.