You do know that NPCs can, you know, move around, right? That the 1st level ones won't just sit there to be killed, and the higher level ones won't wait for the monster to come to them?
Sure. That's why it probably took years to depopulate the city.
Yes, so the leader *himself* will give it a run for its money. But, clearly he's not alone. Any leader of a nation (the dwarves considered it so) would have a personal guard who were quite capable. And the dwarves are a militant race, so certainly they have security forces that are well above 1st level. There's going to be a whole bunch of combat capable characters in that city. If we accept Durin the top at 9th, then there's going to be enough 5th level characters to fill a mead hall. As soon as the Balrog comes a-callin', they're going to come out, and in aggregate they will take it down handily.
I'm fully prepared to except that there were many NPC's above 1st level in a city as great as Dwarrowdelf. Let's say the whole holds 20,000 dwarves, equivalent to Medieval London or Paris. I'm prepared to believe that there were hundreds of dwarves of 4th level or above, given both D&D demographics regarding dwarves and apparent Tolkien demographics. What I'm not prepared to believe is that any significant fraction of them had magical weapons, and without them they'd been largely or wholly helpless against the Balrog of Moria. Magic weapons just aren't that common in the Tolkien-verse.
Why should we believe that they lacked magical weapons? Because there is evidence elsewhere in the text. First, Gimli himself would have fit the characteristics of one of these King's mead hall dwarves. And not only that he would have been an important and high stature dwarf, and yet there is no evidence he ever possessed a magical weapon, nor did any or many of his kindred. Gimli probably is at the beginning of Fellowship 5th or 6th level, yet lacking a magic weapon, he would have been helpless against the Balrog even discounting the magical abilities of the creature - which are considerable, both in D&D, and presumably in the Tolkien universe as well (as Gandalf's peer in stature).
Similarly, in a universe like Forgotten Realms, when Boromir is presented by Elrond with a new sword as a present, we'd expect this transaction to involve a magic weapon. After all Elrond is defacto High King of the Elves remaining in Middle Earth (though entitled to claim the honor, he declines to do so), and Boromir is the prince designate of one of Middle Earth's most powerful kingdoms. But, the text gives us no reason to think this is actually the case, as the troll that tries to enter the chamber of Marzarbul seems completely immune to Boromir's weapon, and only Frodo's Sting - explicitly known from the text to be magical - is capable of biting that magical flesh despite Frodo's much weaker arms and lesser combat prowess. In other words, Boromir hit the thing, but couldn't overcome it's damage resistance, likely because his blade wasn't magical.
Also, Tolkien dwarves, unlike D&D dwarves, can't actually see in the dark. And an anti-Gandalf certainly would have had the power to fill tunnels with darkness, and extinguish fires and flames - powers largely reflected in the 1e type 6 with its ability to create darkness at will. Early on it can act like a perfect ambush predator, killing off dangerous dwarves as it encounters them, and fleeing if (rarely) threatened. Because it can detect magic at will, it knows when it can be threatened so its never going to jump into a fight were the odds aren't in its favor. The D&D version can use Symbol of Death to kill off individuals or even dozens of dwarves at a time - magic items or not - with no risk to itself, and it has other useful spells as well that I can't recall at the moment.
Gradually, as the heroic leaders of the community are killed off, it can take the offensive. Any dwarf without a magic weapon is toast, which was always most of them and by this time is almost all of them. The majority of foes won't even last a round, even if they had an ax +1, and he can kill off a half dozen at a time with ease. Of any 100 or so that try to band together to stand against him, a significant portion will end up fleeing or cowering in terror because of his aura of fear. In short, yes, a type VI demon in 1e really can kill off a whole city of dwarves using D&D demographics if you only assume that magic items, and especially potent items, are very rare in the particular campaign world.
It is not clear that the axe disappeared with Durin. All we know is that Balin's people found it - it could have been lost with Nain, Durin's son.
Fair point. All we know is that it wasn't successfully employed against the Balrog, who (certainly in D&D) had several abilities that would effectively thwart any would be wielder of it - flight (assuming wings), a vorpal blade, symbol of death, magical darkness, etc.
You don't need "the average" to be 6th. You need, maybe, a dozen such in the entire city, who would be called on when such a monster reared his ugly head.
DR 10/magic is a 3e innovation. In 1e, if you don't have a magical weapon, you are just out of luck against anything even as lowly as a gargoyle.
In essence, this argument assumes the conclusion - Gandalf is only a 5th level wizard...
No, Gandalf is only about a 5th level wizard because he never casts any spells above 3rd level, and additionally if he could have cast higher level spells then the story becomes problematic because higher level D&D spells can do things far beyond the observed abilities of anyone in the story. The only character that seems to have these higher level spells is Sauron, which neatly suggests just why he is so feared.
because we assume the demographics to be not just "most" NPCs are first level, but that characters of notable level in the population are nigh non-existent. I suggest that this is backwards. We should look at what happens in the books, and track back to what that means in D&Disms.
That's precisely what I am doing. Again, I think the critical point involving combat with a Type 6 demon in D&D terms is that magic items are rare, and that once the few high level characters that have them are assassinated, the rest of the community goes into an unrecoverable death spiral against any creature that requires a magic item to damage it.
Smaug is as big and old as dragons get. Balrogs are not far short of such a dragon (by description of combats in which they are featured). Work down from there.
Sure. But Smaug as say a 10HD ancient red dragon is harder in 1e AD&D to explain killing off a city of dwarves than a Balor is, simply because a 1e red dragon would run out of breath weapon long before the city ran out of dwarves, at which point those mead hall dwarves you mention start becoming very significant. Of course, if we assume Smaug used a later innovation of being able to split up his breaths into mini-breaths, or like 2e or later could breath once every 1d4 rounds, this problem goes away.
Stepping back a bit, you can get into the Tolkien mindset I think by consider Beowulf, a text Tolkien loved and translated. Those mead hall warriors of the Danes weren't simply 1HD weaklings. The problem was that Grendel was immune to their weapons. Slash and fight back however they might, they couldn't kill the thing. The same issue threatens the dwarves of Dwarrowdelf when faced with the creature from the black pit, who will eventually cause the name of the city to be changed.
