At a young age Masters watched his parents get murdered by some looters. Wanting and seeking justice this young man grew to be a man and tracked the men who killed his parents. Calling himself the Cactus Kid, he shot and killed them. Arrested and pardoned, he went on to Medical school and settled in Leadville, Texas. Now nick-named Doc by the local town folk. Morris led a good life, until he came across a land robber, not wanting to tarnish his reputation he became the Black Rider.
The Black Rider was famous in Brazil where he starred a 245-issue run with 14 annuals and 2 specials, with the title: "Cavaleiro Negro",by publisher RGE. Mattew Master was renamed "Heron Robledo",
When the american material was over, RGE began to publish original stories created by brazilian writters and artists. They also used stories of the characters Durango kid and Gringo and replaced those characters in the stories with Black Rider.