Great Serpent is set apart as a Dragon Type from the Wurm Dragon Type because the Wurm is tied to specific historical culture and proportion. The Great Serpent Dragon Type applies when the dragon falls outside of those constraints.
A Great Serpent may be considered an ancestor or totem animal of a particular group or family. It may be the great guardian of a local well, watering hole, or sacred field. A serpent that is named either because it is revered and respected or feared and killed is considered a Great Serpent.
The Great Serpent type need not be of spectacular size or terrifying shape. Great Serpents may be enormous or tiny specimens, sometimes with particular attributes, such as horns or antlers. In most cases, a Great Serpent is set apart from other snakes by the simple fact that it is imbued with important powers or wisdom, usually over human life or natural phenomena.