Showrunner Angela Kang isn't saying who the masked mystery man is on The Walking Dead, but she's saying who he's not: a character from the comic book with ties to those armored soldiers introduced in the Season 10 finale. "A Certain Doom" saw Maggie (Lauren Cohan) return to Virginia after years away, reuniting with her friends alongside a metal-masked bodyguard who used his bladed kama weapons to rescue Father Gabriel (Seth Gilliam). This nameless warrior character will be unmasked in the Season 10 bonus episodes airing early next year, where a new story reveals what happened to Maggie during her time away with Georgie (Jayne Atkinson).
Kang confirms with Insider that the masked man is not Mercer, a Marine turned Chief Officer of the Commonwealth Army. These were the white armor-wearing soldiers who ordered the surrender of Eugene's (Josh McDermitt) group when they reached their rendezvous point with Stephanie's people (Margot Bingham) inside a rail yard in Charleston, West Virginia.
Due to his high rank in the Commonwealth military, Mercer has connections to Pamela Milton, governor of the Commonwealth, and Sebastian Milton, her spoiled son. The Miltons belong to the upper-class of the Commonwealth, a sprawling network of towns home to nearly 50,000 survivors categorized into high or low class.
More about the mystery man will come to light in the episodes ahead, as the six new bonus episodes build a bridge to the Commonwealth story driving the eleventh and final season of The Walking Dead.
"I'll say that we will learn more about this character and kind of who they are and what Maggie has been through more recently," Kang said. "That's going to be a big part of the story in the six episodes to come, but also in the season  as a whole to come."
Should the show follow the comic book, spoilers, Mercer's live-action counterpart will forge a special bond with Juanita (Paola Lazaro), a.k.a. Princess. The comic book saw Mercer grow loyal to Rick Grimes, who he identified as the best person to oust Pamela and replace her as the leader of the Commonwealth.
Rick (Andrew Lincoln) is currently MIA and in the custody of the Civic Republic Military, the helicopter group who flew away with Rick in season nine. Walking Dead chief content officer Scott Gimple previously confirmed the Civic Republic and the Commonwealth are two separate civilizations.