Originally, this horse thief discovered the Friends through a dumb luck-induced encounter with Mirage and decided to join them out on a whim. His soul collecting was through his "trouncing" of the sheriffs of Rickety Gulch by putting them in a sack and beating them to death with his hooves. Thankfully, Piglet managed to show him the light by radiating the pure magic that compromised his body, through a very awkward Heel-Face Turn. Guess who's the NEW sheriff of this town?
Of course, it's Nasty Jack! (The "nasty" refers to his power alone now)