Region of origin: Brazil
A creature living in Brazilian lakes and other large bodies of water, the iara would lure men into the water with hypnotic songs, where they would live with and serve her. While the iara are immortal, their thralls would grow old and die as normal at which point she would seek out a replacement. Origins for the iara lore exist as one way of explaining what happened to people who had wandered into the jungle and never returned, and developed over time from a mixture of river monsters from traditional indigenous Brazilian mythology and the stories of European mermaids brought over by Portuguese settlers.
Originally posted on Tumblr on May 25, 2016