Ur-grues are thought to be the shades of fallen Implementors. Skilled in black sorcery, the ur-grue can envelop itself in a personal zone of darkness which neither lamp nor flame can penetrate. Sunlight is the only thing it fears. It is unwise even to speak of this utterly evil entity.
In the year 966 GUE a humble peasant stumbled into the lair of this creature deep under the Mithicus Mountains, and was able to discover that an ur-grue is actually an Implementor (resembling nothing more than an old man) who had assumed control of the body of a grue, and was using it as his guise. This particular ur-grue was noteworthy for his theft of the Coconut of Quendor from his former companions, the Implementors. Although his motives are unclear, it is possible that this ur-grue hoped to seize control of the entire world.