A Polyglot can speak languages instinctively just from hearing them and can mimic other peoples' voices, though elves with other abilities can learn to mimic as well. Polyglots often have another special ability.
Sophie Foster - Sophie first discovered she's a Polyglot when she was in Paris and she spoke French.
Lady Gisela - Keefe's mother
Councillor Clarette - She controls the arthropleura on Sophie's escape from exile. She is arguably the most powerful polyglot the elvin world has ever known and has had hundreds of years of practice.