Mason (Callum Blue) (1939 - 1966) claims he was born at a rock and roll concert behind a stack of amplifiers and died drilling a hole in his own head seeking a permanent high. Mason is originally from London (he reaped Rolling Stones guitarist Brian Jones in 1969) and was transferred to his present location some time ago. He lies regularly about his past, such as in his claim of being born at a rock and roll concert (despite being born circa 1940) or that he has never been on an airplane (presumably to explain getting wasted before the flight). He is the only Reaper besides George whose doppelgänger has been depicted, by Canadian actor Jacob Chaos.
Mason collects money from the dead, steals from the living, deals, smuggles and uses drugs. He was an alcoholic and drug addict before he died, and though on at least one occasion he attempted to become sober, has continued these habits in response to the pressures of his job. He is attracted to Daisy, and is often protective of her. He became jealous when she became attracted to another man called Ray (Eric McCormack), whom Mason felt was dangerous; Mason eventually killed him while trying to protect her. While he is drawn to attractive females, his feelings for Daisy seem to run much deeper. He has an edgy relationship with Rube; they dislike, but tolerate each other. Rube has on more than one occasion referred to Mason as an "idiot" or a "fuck-up", but Mason seems to at least want to gain Rube's approval.
Despite his portrayal as a criminal and a degenerate, Mason seems to have genuine compassion for the decedents he's assigned to, and on more than one occasion has helped them out after death in settling their affairs or arranging their bodies to prevent embarrassment or emotional pain to their families. This is perhaps a nod to Mason's emotional growth during the series. He's also one of the only reapers to never talk down to George throughout the series.
Mason is the only one among the group of reapers who was visibly pleased that Rube has moved along and is no longer part of the team.