He is a member of the Assassins' Guild in Ankh-Morpork. He teaches Strategy and Poison Theory to students assassins and is known by students as old Mericet. He has been known to examine students as they attempt to complete The Run as has a reputation amoungst the students as being a particularly harsh examiner. He was responsible, with the assistance of another unnamed Assassin, for conducting the examination of Pteppic.
During his career Mericet has broken several records including the record for number of kills. It is rumoured that Mericet is responsible for the assassination of one of the previous Patricians of Ankh-Morpork.