The Grue is a sinister, lurking presence in the dark places of the earth. Its favorite diet is either adventurers or enchanters, but its insatiable appetite is tempered by its horrible fear of light. No grues have ever been seen by the light of day, and only a few have been observed in their underground lairs. Of those who have seen grues, few ever survived their fearsome jaws to tell the tale. Grues have sharp claws and fangs, and an uncontrollable tendency to slaver and gurgle. They are certainly the most evil-tempered of all creatures; to say they are touchy is a dangerous understatement. "Sour as a grue" is a common expression, even among themselves.

In former days it was believed that all grues were eradicated from the face of the world during the time of Entharion, many by his own hand, and his legendary blade Grueslayer. It is now known that uncountable hordes of grues escaped the blade of Entharion and lurked in the bottomless pits of the underground, until they were accidentally released in 883 by a peasant who would eventually become the first Dungeon Master. At this time the grues quickly spread to every part of the Great Underground Empire, including passages underneath Festeron, Antharia. It is there that a Festeron postal worker stumbled into the nesting place of a family of grues. A close call on the part of this postal worker demonstrated that only the mother-instincts of a female grue are strong enough to overcome a grue's fear of light.
An interesting historical footnote concerning grues is the fact that one grue lair was, for many eons, the resting place of one of the Cubes of Foundation. In order to recover this cube, in 966 the Head of the Circle of Enchanters was forced to temporarily turn himself into a grue as a part of a quest that would eventually result in the end of the Age of Magic.

But the grues' association with magical objects doesn't end there. Sometime between 948 and 950 GUE, a gaggle of grues managed to steal the Skull of Yoruk, which they hid in their secret breeding ground underneath the Historic White House. A brogmoid named Brog infiltrated the breeding ground and swiped the Skull.