(n.) One who connives.

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