The Collaborative International Dictionary of English v.0.48:

Tempter \Tempt"er\, n.
   One who tempts or entices; especially, Satan, or the Devil,
   regarded as the great enticer to evil. "Those who are bent to
   do wickedly will never want tempters to urge them on."
   --Tillotson.
   [1913 Webster]

         So glozed the Tempter, and his proem tuned. --Milton.
   [1913 Webster]

WordNet (r) 3.0 (2006):

tempter
    n 1: a person who tempts others; "Satan is the great tempter of
         mankind"

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "tempter":
   Circe, Don Juan, Lorelei, Parthenope, Siren, abettor, actuator,
   animator, cajoler, charmer, coax, coaxer, coquette, enchanter,
   enchantress, encourager, energizer, enticer, femme fatale, firer,
   flirt, gadfly, galvanizer, impeller, inducer, inspirer, inveigler,
   mover, moving spirit, persuader, pleader, prime mover, prompter,
   seducer, seductress, siren, spark, spark plug, sparker, stimulator,
   teaser, temptress, vamp, vampire, wheedler