For the languages in Age 2, we sought to get actual speakers to do the voices for the units in each civilization. I was in charge of doing it for The Conquerors, which had Spanish, Mayan, Korean, Aztecs, and Huns. It was trivially easy to get Spanish and Korean of course. I used Brigham Young University as my go-to source for obscure dialects. BYU has a huge language department, because all the LDS missionaries who travel to far-off lands and return having learned Quechua, Laotian, Tagalog, Poli