There was a pretty big clue on John Legend's Instagram page earlier: @NBCTheVoice Mega Mentor for Season 17 is VERY MEGA. If only @blakeshelton and I could figure out who it is. 😂
Hint, it's not her first time on the show, she was there season 7 too, during the knockout rounds. Yep the one and only Taylor Swift is back and bigger than ever, as a MEGA Mentor on the show this season!