Kist Magg Thek Lutiven-Day Slitheen (also known as Tim Jeffrey) is a member of the Slitheen Family, Korst Gogg Thek Lutiven-Day Slitheen's father, Glune Fex Fize Sharlaveer-Slam Slitheen's brother and the secondary antagonist in The Sarah Jane Adventures episode Revenge of the Slitheen. In his human disguise of Tim Jeffery, he is portrayed by Ian Midlane, who also voices his true form which is portrayed by Paul Kasey.