- Real Name: Arthur Brown
- Alias: Cluemaster, Aaron Black, The Reformer
- Identity: Secret
- Alignment: Bad
- Gender: Male
- Occupation: Professional Criminal
- Affiliations: Formerly Suicide Squad, Injustice League II, Justice League Antarctica, Legion of Doom
- First appearance: Detective Comics #351 (May, 1966)
- Universe: Earth-One, New Earth
Arthur Brown was a failed game show host who turned to a life of crime, leaving trademark clues as to his actions. He is frequently imprisoned in Blackgate Penitentiary, and also has an estranged daughter, Stephanie Brown, alias the masked vigilante Spoiler. Although Spoiler was originally inspired to take up her costumed identity as a means of combatting her dad (and spoiling his plans), she would eventually turn into a full-fledged crimefighter.
Cluemaster has had a long criminal career not just limited to Gotham City, at one point joining the second incarnation of the Injustice League, which would later develop into Justice League Antarctica.
In an effort to become pardoned for his crimes, and finally gain his daughter's respect, he joined the Suicide Squad on a counter-terroist operation to Iceland. He saw most of his Injustice League buddies killed, and Cluemaster was apparently deceased, shot many times through the chest. However, he miraculously survived (he saved the life of comrade Major Disaster twice, who later noted that the situation had been very confusing), and spent nearly a year recuperating in a hospital, comforted by thoughts of his daughter.
When Brown finally arrived back in Gotham City, he learned of Stephanie's "death." Overwhelmed with grief, he attempted to bring Batman to what he perceived as justice for the death of his daughter at the hands of Black Mask during the events of War Games. He took on the false identity of Aaron Black, The Reformer, and accused Batman of being guilty of child endangerment, having had previous Robins die on his watch as well. In doing this, he formed the "Campaign for Culpability", which eventually led to a verbal confrontation with Batman.
Cluemaster finally reappears after Stephanie Brown has become the new Batgirl. He is revealed to be the man who has been funding the Reapers, a group of young supervillains who have been battling Batgirl.