In The Walking Dead comic books, The Whisperers are a creepy-as-fuck group of humans who disguise themselves as zombies and wander the tortured earth with a greater sense of purpose and directive. In the television series, however, they're only now being introduced, and are positioned as the next major antagonists for our eternally beleaguered group of survivors.
AMC teased The Whisperers in the trailer for the mid-season finale for Season 9 (titled, ominously, "Evolution.") You can watch it above. As always, the only thing worse than a herd of zombies is a crazy cult of weirdos that dress up like zombies. The episode airs this Sunday, November 25th.