The Ur-grue is revealed to be the primary villain of the story. The player, sent to retrieve the Coconut of Quendor from the Implementors, arrives at the Implementors' Luncheon on the Ethereal Plane of Atrii only to find he has been followed by the Ur-grue in shadow form, who takes the opportunity to steal it for himself. The player must then venture into the Ur-grue's extensive underground lair and retrieve it. The Ur-grue is shown to be a dungeon master of sorts, controlling huge parts of the "Zork" underground and having accumulated an enormous hoard of treasure, of which the Coconut is his crowning acquisition. He has not only an army of grues at his disposal but also bizarre creatures of evil such as Lucksuckers, spirits who attack the player by draining his good fortune (reducing his Luck stat). The Ur-grue himself is surrounded by a pool of magical darkness that is capable of overcoming and destroying all artificial light sources, and is therefore only vulnerable to pure sunlight—the player, therefore, can only best him by using a series of mirrors to transmit a beam of light at him from outside the dungeon. After doing so, the Ur-grue's shadowy form is dissipated revealing what may be his true form, that of a broken, withered old man. It is implied that the Ur-grue cannot survive long in this form and must possess others' bodies, like a demon, in order to survive—he attempts to possess the player. If he succeeds, a negative ending is revealed where the possessed player-character finds and strangles baby grues until he finds one strong enough to hold the Ur-grue's essence, implying that the Ur-grue's usual shadowy form is an enhanced version of a grue's body. If the player's Compassion stat is high enough—represented by having done enough good deeds throughout the game—the Ur-grue is shown to be unable to possess the player, his evil apparently unable to coexist in the same body with an extremely pure or virtuous spirit, and the Ur-grue's old man form fades away. Whether this means the Ur-grue was permanently destroyed in this encounter is unclear, as is the possibility of others of his kind existing somewhere in the world, although, being magical in nature, it seems unlikely any Ur-grues could survive in Quendor following the Great Change. Almost since the company's beginning, Infocom's games included "extras" (called feelies) in the packages, often serving a dual purpose of entertainment and copy protection.