The tavern is close to, but not directly on, a trade route between the Yjsbson Empire in the south, and various barbarous northland kingdoms in the north. During the summer months, there will occasionally be merchants, tradesmen, fortune-seeking barbarians, army deserters, spies, assassins, and all sorts of other interesting people stopping overnight at the tavern. I'll put an encounter table up in due course. For information on the surrounding wilderness (including an encounter table) see here.
There will also be several gangs of adventurers arriving in the next few days, looking to explore the disused mines below the tavern. It would be appropriate to introduce any additional player characters at this point.
Some of these adventurers will have come in answer to advertisements in Megalopolis, Atlantis or Qwanet, asking for people seeking adventure. Contrary to appearances, these advertisements were not posted by Rjspldhmba the Pervert. They were, in point of fact, posted by agents of General Afschrlyyjlvrmllo, who is recruiting an army.
Rjspldhmba does not know exactly who is recruiting adventurers, or why. He does know that anything going on that he does not know about is probably not done for his benefit. On the principle that it is always best to put spokes in the wheels of other people's plots, he bribed the wizard Kroffilkovin, who was supposed to take the recruits to General Afschrlyyjlvrmllo, to take them to a teleport marker near the tavern instead. Rjspldhmba himself led the novice adventurers to the tavern. He has no particular interest in what they do next, as long as it is not anything which would inconvenience him.
At that point, the characters will presumably wish to explore the maze.
Just accept that it's unpronounceable and impossible to learn.
OK, if you really can't accept that: a bard or diviner with both ancient language and modern language skills could learn it by devoting three language slots to it. It's a very difficult language.
Local plant life is poisonous to all but the locals. Don't eat it. If a character does eat local plants, make him regret it. If he does it again, kill him.
Plant pollen is also poisonous, but this isn't important in mountainous regions except near the spring equinox.
The meals in the tavern are badly-cooked, but the real danger is the ingredients.
Dead herbivores (e.g. rabbits) have the remains of local plant life in their bodies.
(AD&D-specific:) Anyone eating boiled rabbit, or any similar meal, must make a constitution check overnight. Anyone succeeding merely suffers the indignities of horrible griping pains and diarrhoea. Anyone failing is out of action for the following day - no adventuring, no memorising spells, and any attemped action will result in a fumble. Anyone making two consecutive constitution checks has acclimatised and no longer has any problems (and need not make further checks).
(AD&D-specific:) The problems are worse for non-humans. In addition to the constitution check, non-humans suffer damage overnight, as the horrible meal makes its way through their system. Half-elves suffer 1d8 damage. Elves suffer 2d8 damage. Dwarves, gnomes and halflings suffer 2d4 damage overnight.
Dead carnivores (e.g. wild dogs) are safe to eat. But they're not safe to catch. If adventurers catch wild dogs, the tavern staff will help to cook them (and do their usual unappetising job), but the tavern staff will not assist in any attempt to catch wild dogs.
Everything Nmjjpjjro says is true, to the best of his knowledge.
Nmjjpjjro does not actively look for trouble, but this part of the mountains is not entirely free of danger, and trouble may come looking for him. (AD&D-specific:) Nmjjpjjro is roughly 9th level at the moment. He will advance in level more slowly than the player characters.
Nmjjpjjro's principal limitation is that he serves a false god. Pnmjje the Munificent, God of Commerce, is at best a demigod. (AD&D-specific:) Nmjjpjjro will not be able to cast 6th-level spells even if he should reach the appropriate levels.
Nmjjpjjro is lawful neutral. His sect believes in price controls. This will clearly disappoint those who believe that free market economics is the one true faith. However, it does mean that he will cast healing and curative spells for anyone who pays the standard price.
While he will not say anything untrue, Nmjjpjjro may at times be selective in the truth. He hopes that groups of adventurers will explore the disused mines. He knows that, as a result, many of them will be injured or poisoned, or catch diseases or curses. This is the point. When they do, they will come to his temple for cures (or, in emergencies, a priest can be called from the temple to the tavern). The temple will do lots of profitable business, and the prestige of Pnmjje the Munificent (and Nmjjpjjro's career) will be enhanced.
Rjspldhmba the Pervert has various reasons for staying at the tavern, in addition to those which Nmjjpjjro has mentioned.
Firstly, he is researching a spell, Rjspldhmba's Great Reflection. This work is expensive, and he is seriously short of funds. If the characters catch something which necromantic magic might cure, Rjspldhmba will offer to do so. He charges the same as Nmjjpjjro, but it takes only a few minutes to call Rjspldhmba to the scene, whereas it usually takes a few hours to call Nmjjpjjro. The work also consumes mirrors as material components; every now and then, Rjspldhmba will offer to buy a mirror, if necessary offering rather more than the going price.
Secondly, Rjspldhmba the Pervert thinks he might have enemies in the disused mine. He knows that the tunnels go a lot deepr than Nmjjpjjro suspects. A few years ago, he was part of an adventuring party exploring them. He and they fell out over something (perhaps they couldn't agree who was the evillest and most perverted), and he returned to the surface while they took up residence deep down below. If a group of characters appears to be reasonably successful, Rjspldhmba might offer them a few hints about what they might expect as they progress to deeper levels.
Thirdly, Rjspldhmba is descended from the family which once ruled the Yjsbson Empire. He hasn't ruled out the possibility of returning to the capital at the head of an army of undead and setting himself up as Emperor. He doesn't see the Empire as "rightfully his", because the concept of anything belonging to anyone as of right is not one which he buys into; it's more "because it's there". So he remains at a location which is on the borders of the Empire, not exactly inside it, but not exactly outside it either.
Although Rjspldhmba the Pervert is chaotic evil and proud of it, in the immediate future he won't do anything which would bring him into direct conflict with Nmjjpjjro's sect. Rjspldhmba has enough enemies as it is.
(AD&D-specific:) Rjspldhmba is roughly 11th level at the moment. He will advance in level more slowly than the player characters.