(n.) One who plots or schemes; a contriver; a conspirator; a schemer.

Benedict Arnold Brutus Judas Judas Iscariot Machiavellian Quisling archtraitor betrayer cockatrice coconspirator conniver conspirator conspirer counterplotter double agent double-crosser double-dealer exploiter finagler informer intrigant intriguer machinator maneuverer operator opportunist quisling rat schemer serpent snake timeserver traitor treasonist trimmer turncoat wire-puller