The shrieker is a monster in NetHack. According to Dungeons and Dragons, the shrieker is a large purple fungus. While it has no attacks and moves very slowly, its ability to shriek gives it the ability to aggravate monsters and occasionally (1/10 of all shrieks) summon a random monster somewhere on the level, 1/13 of which are purple worms (the explanation given for this is that purple worms enjoy consuming shriekers and are attracted by their shriek). #Chatting with a shrieker will also cause it to shriek; this aggravates monsters, but cannot summon any. The shrieker corpse also gives a 20% chance of poison resistance, and is safe to eat (unless they are rotten); further, as the shrieker is considered a fungus, consuming a shrieker corpse does not break the vegan or vegetarian conducts.
The line "The shrieker shrieks." has gained a reputation as being one of the most memorable lines in NetHack.
In SLASH'EM shriekers, like all F except lichens, may rise from the dead. Additionally, they are incapable of summoning purple worms but are slightly more likely to summon a monster with a shriek (1/8 chance instead of 1/10). The first change may be because two other monsters, the squealer and the mobat, have the same shriek in SLASH'EM. They are also immune to death rays, strangely enough.
With a single, savage thrust of her spear, the warrior-woman
impaled the fungus, silencing it. However, it was too late:
the alarm had been raised[...]
Suddenly, a large, dark shape rose from the abyss before them,
its fetid bulk looming overhead...The monster was some kind of
great dark worm, but that was about all they were sure of.