1) Cabal participant 2) Lowdown sneak 3) One colluding 4) Underhanded one 1) Schemer 2) Sneak 3) User 
Conniver (1944–1970) was an American Thoroughbred racehorse who was voted the 1948 American Champion Older Female Horse. Bred by Alfred G. Vanderbilt II, she was purchase as a yearling by New York City businessman and sculptor, Harry La Montagne. When her racing days were over, Conniver was used as a broodmare. Of her six foals, Clandestine and ...
• (n.) One who connives.
Con·niv'er noun One who connives. 
conniver Someone who connives or plots.