A grue is a grisly little comic poem with sadistic content and trick last lines. They are sometimes known as "Little Willies" because of the "hero" of many of them. The word was coined by no less a personage than Robert Louis Stevenson, from "gruesome".

Although their content is certainly no worse than the daily news, most grues are anonymous.

Willie poisoned father's tea
Father died in agony.
Mother looked extremely vexed;
"Really, Willie," she said, "what next?"

A color, usually defined (prior to January 1, 2000), as meaning "green before 1/1/2000, and blue afterwards." (Of course, now that it's later, philosophers everywhere will have to use a different definition. It was invented decades ago). Alleged to be the color of emeralds in Nelson Goodman's "grue-bleen paradox."

grovel = G = grunge

grue n.

from archaic English verb for `shudder', as with fear The grue was originated in the game Zork (Dave Lebling took the name from Jack Vance's "Dying Earth" fantasies) and used in several other Infocom games as a hint that you should perhaps look for a lamp, torch or some type of light source. Wandering into a dark area would cause the game to prompt you, "It is very dark. If you continue you are likely to be eaten by a grue." If you failed to locate a light source within the next couple of moves this would indeed be the case.

The grue, according to scholars of the Great Underground Empire, 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 extreme 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 have 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 grues themselves.

All this folklore is widely known among hackers.

--The Jargon File version 4.3.1, ed. ESR, autonoded by rescdsk.

Amusingly enough, in the game ADOM (Ancient Domains of Mystery, a freeware ASCII Roquelike game, in case you don't feel like reading up on it) the grue makes an appearance, which obviously alludes to its appearance in Zork. Actually, come to think about it, it doesn't really make an "appearance", since it's never seen—but that's not the point.

The point is that, in a similar fashion to Zork, a message somewhere along the lines of:

It is dark. You are likely to be eaten by a grue.

... is displayed when entering a dark tile.

From reading technical texts on the game, the possibility of actually being eaten by the Grue (instant death) is 1/1000. Now, this may seem like ridiculous odds, but take it from one who actually had the willpower and time on his hands to complete the game: It can happen. Anyone who has played ADOM can tell you that moving through 1000 tiles (and thereby risking the odds) can be done in a matter of minutes.

So needless to say, pack a few torches, or learn the Light spell.