Back in December 1978 Dragon magazine issue#21 had hit the news stands & there's a Don Trumball dungeon section that's called THE HALL OF MYSTERY
A section deep in the Greenlands Dungeon By Don Turnbull - Cambridge, England. What use is a section of a dungeon?!
'The Hall of Mystery' certainly has a ring to it doesn't it? And this is where I think it could be used as a legendary dungeon location that could be dropped into your own own campaigns. And this is where the dungeon has implications within OSR campaigns.
For a game such as Adventurer, Conqueror, King rpg 'The Hall of Mystery' might be one of those legendary locations of Law. A place that has fallen away into the mists of time. The hall has become ancient beyond time as it was the resting place of past kings. And is now the domain of humanoid of Chaos. Because of the dungeon section's connection to the King Arthur legend this is a deadly dungeon even by ACK's standards.
The Hall of Mystery is another of those dungeons that could be transported into the Lion & Dragon rpg because of it's connection with the Arthurian legends. My own only concern is the fact that the dungeon is quite nasty & dangerous. So 'The Hall of Mystery' has the potential to hide some major Arthurian artifacts from another age.