Squire Flanagan is a man who lives in the woods in Forest Survivors, who was originally the one that posessed the Knife of Ages.
During the movie, it is presumed that Chase Cinder and his partner raided the camp. This would explain that why only a little while later in the movie, Squire Flanagan pursues Joshua Wilder, who is dressed up as a raider.
Squire Flanagan shoots at Joshua, then knocks him unconscious. According to Dorian Moe, Squire Flanagan unmasked Wilder, realized he wasn't a raider, and fled.
He does not return.
Not much is known about Squire Flanagan's true nature, as his mindset is altered after the Cinder raids his home. Apparently, however, he does not understand the true power of the Knife of Ages, because he simply hands Broad Petersburg the key to its chamber.
Viktor Klov was originally supposed to be Squire Flanagan in disguise, but the idea was scrapped and they became two separate characters. They are, though, portrayed by the same actor.