Black Mask

Roman Sionis, also known as Black Mask, was the leader of the False Face Society and encountered Batgirl while she was patrolling. Black Mask leads the False Face Society, a ring of zombie-like villains wearing grotesque masks that threaten to take over the city. He is presumably stopped by Batgirl.

Biography
At some point, Black Mask stumbled upon Batgirl while she was patrolling the streets. He and his gang, the False Face Society, threaten to take over the city. Batgirl had to make a decision whether to continue being Batgirl or continue being a normal teenager in Gotham. She presumably decided to continue being Batgirl and continue fighting crime, and she presumably stopped Black Mask.