Something is killing and eating the people of Th'gil. This monster displays cleverness, strength, and a thirst for blood. The PCs have stumbled into this town. Will they leave by walking or by dieing?
From that silent place fear flows in unseen waves, like white fog. The shadows are many, and the wind breathes cold through the broken battlements and casements. Through it's frowning walls and dark window openings there's a lantern of the spirit which none see by but those who bear it.
In local legend, the Halls are fairly old, with stories of people disappearing going back for hundreds of years, said to be taken by the Faeries. In actuality, the Halls are much older.
"What you wanna go messin' around up in the mountains for? Ain't nothin' up there but snow, and wolves, and more snow.
Yer lookin' for the old tomb? Take my advice, boys. Let that tomb alone. There ain't nothin up there you ought be messin' with. No money, no treasure, no fame, just ice. And death."
Not named for an resident beast, but for the multitude of winding, mazelike passages fraught with danger.
When running a new party, get around the question of plot density by having the first discovery to be a deck of fate, or whatever you call it. If you use a real deck, you should definitely stack it to have the desired outcome, which is to curse the party to attract weird things to happen and involve them. This should not be told to the players at the time, so that they won't just up and try to get themselves 'decursed'. Though quite why they would want to is beyond me.