For those that have played Nethack, you'll know what Demogorgon is: Arguably the most powerful demon-prince in that game, rated even more difficult than Death, Famine, and Pestilence.
In a normal game of Nethack you are unlikely to ever encounter Demogorgon because he doesn't spawn directly; he must be summoned by a lesser demon, or another demon prince. A typical encounter by an unprepared player with Demogorgon goes something like this:
You miss Demogorgon.
Demogorgon stings!
You feel very sick.
Demogorgon stings!
You feel worse!
Demogorgon casts a spell!
Dreadful wounds appear on your body!
Demogorgon hits!
You zap the wand of death!
The death ray hits Demogorgon!
Demogorgon is uneffected.
Demogorgon stings!
You die from your illness.
What makes him so deadly is he has two attacks that cause deadly sickness, as well as generally hitting very hard anyhow, AND having the ability to cast high level magic, possibly even summoning other demon princes to his aid. The sickness attacks are the worst part, if they are not cured immediately the effects will stack with each other and you can be dead in less than five turns.
After fighting a Giant Cave Spider last night I was immediately reminded of Demogorgon... simply because it has so many insta-death ways of killing you. If you are lucky and don't get instantly paralyzed by webbing, then it will bite you and you will almost instantly be paralyzed by poison. From that point on it could nibble you to death if it wanted because you are completely helpless.
I'm perfectly okay with having nearly unbeatable enemies in the game, in fact it was quite thrilling to actually engage a GCS in melee combat and win (even thought it was by pure dumb luck.)
... However, I would expect such an epic foe to be a little less common. As it stands I more often than not run into at least one in every cave, and usually more than one. My wife had a good laugh at me the other night because I had just barely survived a spider encounter only to run into another one just around the corner.
The chances of even another demon prince summoning Demogorgon are less than 1/200, so the chances of running into him (unless you are trying to) are pretty low.
Why are Giant Cave Spiders so common?
[ January 26, 2008: Message edited by: Coriantumr ]