OK, here's my first attempt at this thing. First post is the backstory, second post is the mechanical stuff, third post is questions I've got for Dejoker.
Wilson Burke was the son of a traveling preacher in a small town in northeastern Texas. His father was often gone for work, leaving him with his mother. His mother passed when he was 10, and he often fended for himself, whether earning money at odd jobs or (often) getting into trouble. With his father mostly absent, he was essentially raised by the keeper of the small chapel, Joseph. Whenever his father came home, he taught Wilson, usually Bible stories, but also how to read/write, basic math, and told him no end of tall tales (usually after a few drinks, and Wilson eventually stopped believing them) about horrible creatures and occult horror stories. Wilson eventually rebelled against his father (and Joseph), and having had enough, left town to seek his fortune. Burke found a new life in Louisiana and Arkansas as a small-time crook and con-man. He often gambled and occasionally found himself a part of small-time gangs, occasionally rustling cattle, or in their prime, robbing a train.
Unfortunately, Burke was also spent time in jail, and even after being released, continued a solo life of running cons and cheating at cards. He managed to maintain a certain code of ethics, refusing to kill unless someone attacked him first, and never stealing from women or children. His life of crime eventually caught up with him. He joined a gang that was a part of a much larger criminal organization, and his small-time gang tried to steal from the organization's leader. Most of the gang was killed, but Burke managed to escape. Knowing the organization knew his name and face, Burke high-tailed it back into Texas to lay low in a town near his former home.
When Burke got there, he learned of his father's gruesome death. Not believing the stories, he traveled to his hometown, finding the town in mourning and the chapel burnt to the ground. The keeper, Joseph, told him that his father was inside when it occurred. He didn't know how the chapel burned, but was woken that night hearing his father arguing loudly with someone, but not knowing who. It wasn't long afterwards that he again woke to the building on fire but couldn't get through the flames to Preacher Burke.
Joseph then told Wilson the good and bad news: Preacher Burke had a will that instructed Wilson, as his father's last wish on earth, to follow in his footsteps as preacher, and to finish what he had started. Joseph then let Burke in on the secret of the elder Preacher Burke: While he taught and preached all around Texas, he was also hunting supernatural creatures that would do his flock harm. All the stories that Wilson had been told as a child were true, and as the next in the Burke bloodline, it was Wilson's destiny to continue this work. Wilson was given a box of his father's belongings, including twin Colt Peacemakers (engraved in a language Wilson cannot read) his father's bible and clerical collar, and a large leatherbound book filled with his father's writings.
Wilson immediately recoiled from the whole situation, gathering his things to leave. Joseph kept him there with a single sentence: "I know who you're running from." Somehow, Joseph knew about the botched job, and why Wilson was here in the first place, and threatened to tell the organization where Wilson was hiding if he didn't comply with his father's wishes. After some days of thought Wilson complied, took up his father's clerical collar, and after significant training with Joseph, began to do the Lord's work.
Preacher Wilson Burke travels the old west, doing the Lord's work by preaching, helping others (where he has to), and fighting the forces of evil. He's finding that he enjoys the work more than he expected, but still pulls at his metaphorical leash often. He's often angry at his God at his current lot in life, but fortunately for him, his deity seems to have a sense of humor with the situation (rather than standard angry Old Testament God). Thus far, at any rate, Preacher Burke has not been smote (smited? smitten?) yet, even with Burke going so far as to curse the sky.
Burke knows the other player characters as members of an old card-shark gang that broke up amicably. They've worked together in the past, whether drinking and carousing, gambling (and cheating), or working their next card-sharking con. At the start of the story, Burke will likely have bumped into them again in a mid-size town, and spent some time sharing stories and reliving the old days, Though Burke feels compelled to prevent them from sharking anyone, at least in his direct presence.