One of the deadliest and most brutal villains from The Walking Dead comics will appear on the TV series when season 6 returns in February. Negan will be the most extreme adversary Rick and his group have ever encountered on the show and according executive producer Robert Kirkman, his arrival will change things permanently, and not for the better.

"As far as shake-ups go, we have lots of shake-ups from season to season," Kirkman told Entertainment Weekly. "It keeps things interesting — keeps the blood pumping, I like to say — but Negan is kind of an atomic bomb that's going to be dropped on the show and the show will probably never be the same after that. So buckle up, I guess?"

Negan was introduced in the comics in The Walking Dead #100. He is known as the leader of a nefarious group called The Saviors. Kirkman shed some light on what fans can expect from this new group of villains led by a shrewd and calculating psychopath "who's had his morality dial a few clicks away from Rick toward the darker aspects of his personality".

"I think the Saviors are dangerously organized," said Kirkman. "The Wolves were psychotic, the Hunters [the group from Terminus] had a lot of weaknesses. When it comes to the Saviors, and Negan in particular, the way I've always thought about this in the comics is this is a group that's led by a guy who's had his morality dial a few clicks away from Rick toward the darker aspects of his personality, but is still an intellectual and capable leader who's kept his group alive against all odds just as long as Rick has."

Actor Jeffrey Dean Morgan
Actor Jeffrey Dean Morgan will play Negan in The Walking Dead TV series Reuters

"It's really the best encountering the best. When these two forces come head to head, things are gonna get interesting. This is a much different group than they've ever encountered. The Saviors are a group they're not really prepared for."

The Walking Dead season 6 returns with episode 9 on Sunday 14 February 2016.