Castle Builder System is the name of a range of terrain products primarily designed to create castles. They are made of a durable polymer called "Dwarvenite" by its manufacturer, Dwarven Forge. many pieces are fitted with metal or magnetic parts to assist in interlocking the parts. Some parts have LED circuitry (switch, battery, and socket) to support LED lighting attachments. Some parts are lighted by an LED. This series is compatible with the others series made of Dwarvenite. Some releases in this series are specifically designed to fit with the City Builder System and are annotated as CBS in their part listing. The Castle Builder System comes in painted and unpainted versions.