The Hunter — Stuart G. Yates

Thirty years before the events of He Who Comes, Reuben Cole is a young man yet unforged in the blood of his enemies. His ruthless determination to hunt down those who has broken the law is a force that drives him forward. An ex-army scout, his skills are valued and sought after whenever trouble arises.  When evil men try to seize what others possess, Reuben is called in. No one who crosses Reuben Cole is going to stay around for long. He is the hunter of those who break the unspoken creed of the Old West.