The Faithful was a group of Obsidian humanoid natives gathered by a Vulcan named Sered, presenting himself as a prophet of their deities. Sered (and the Romulans with whom he was in league) convinced the Faithful to commit acts of sabotage against the Starfleet mission to Obsidian, with the promise that Sered would reward them with sweet water, abundant food, and strong children. (TOS novel: Vulcan's Forge)