1) Becky Sharp 2) Calculating one 3) Certain plotter 4) Conning one 5) Conniver 6) Conniving person 7) Conniving sort 8) Conspirator 9) Contriver 10) Devious one 11) Deviser 12) Finagler 13) Iago or Becky Sharp 14) Intriguer 15) Intriguing person 16) Man of intrigue 17) One creating plots 18) One hatching a plot Found on https://www.crosswordclues.com/clue/schemer
Schem'er noun One who forms schemes; a projector; esp., a plotter; an intriguer. « Schemers and confederates in guilt.» Paley. Found on http://www.encyclo.co.uk/webster/S/29