He has drugged Arkham Asylum's inmates, including The Great White Shark, Poison Ivy, Killer Croc, Victor Zsasz, Jane Doe, and The Scarecrow, with a substance that can kill when triggered. Black Mask is quickly acknowledged as the leader of the group when he blows up the asylum, and then prepares for his ascension by destroying Two-Face's and Penguin's reign and becoming Gotham City's crime lord once again. In a recent Batgirl storyline, he had Scarecrow develop a new recreational drug, "Thrill".