This was something I picked up at my local library in the early 90s (pre-1994). I'd been voraciously devouring other novels at the time, so my memories here are incredibly vague.
Here's what I remember:
It was a big enough release to get on the "new releases" table. A mass-market paperback. Probably an American author. Not Koontz, not King.
It involved either Inuit or Native American mythology.
It was set in a cold climate, I want to say Alaska, but maybe the Northwest Territories or even the Pacific Northwest (but that's a stretch).
It's a rural or small-town setting.
The main character was a man, but there was a female lead as well. One or both of them may have been scientists.
There was a dig or some other kind of archaeological site (or similar) where there was a hole/cave/mountain that had some kind of evil radiating out of it. There was some sort of monster or presence associated with it. The town nearby (where our heroes are staying) was affected. There was probably a decent body count, but I have no memory of the creature.
There is an excellent chance it was named "THE [SOMETHING]" or just "[SOMETHING]". It was not a long title. Bear in mind half the horror novels of the period were also named "THE [SOMETHING]".
The title may have had some kind of allusion to Hell or the underworld.
The only passage I can recall is something about the main character admiring the female lead's figure even through some heavy arctic gear (?!) when they meet for the first time.
That's all I can remember. The irony here is that it is clearly forgettable, but I still want to read it again.
UPDATE: It is not Midnight's Lair by Richard Laymon, unfortunately.
UPDATE: It is also not The Abyss, by Jere Cunningham, though the setup is similar.