Tennis star Serena Williams, pictured above during her win at this year’s Wimbledon championships, could be voicing the female Fire Sage briefly seen at the end of The Sting, in The Legend of Korra season 2 episode 7: Beginnings, Part 1. Williams previously voiced Ming in The Day of Black Sun, Part 1: The Invasion, a 2007 episode of Avatar: The Last Airbender - at her own request, she is a big fan of the series!
This is purely speculation - no sources have confirmed this. However, this recently released clip features the Fire Sage speaking and it sounds unmistakably like Serena! We’ll only know for sure when the credits roll on Friday.