The character he is playing is listed in the break down as Michael Todd, although this is not his real name. The character is described as having a friendly sense of humor who also has a dark side stemming from his past. There is no character named Michael in Robert Kirkman's comic book series, except a young child named Mikey.
The Hollywood Reporter speculates that the actor is actually playing the preacher Gabriel Stokes, who first encounters Rick Grimes (Andrew Lincoln) in the 61st issue of the comic book series, just before he meets the canibals known as The Hunters. Soon after their first meeting, Gabriel reveals the "dark lengths" he went to in order to survive, joining Rick's group shortly thereafter. The character is still alive in the comic books.
Season 4 cast members Andrew J. West (Gareth), Alanna Masterson (Tara) and Christian Serratos (Rosita) were promoted to series regulars for Season 5 back in March. Production is already under way for Season 5, which will debut sometime in October on AMC.
Seth Gilliam previously starred on HBO's hit series The Wire, making him the third alum of that show to star on The Walking Dead, following Chad Coleman (Tyreese) and Larry Gilliard Jr. (Bob). The actor also appeared in Oz , Homeland and The Good Wife.