This is an adventure idea that I was toying with for some time. Note that it fits the default ACKS setting or similar settings and not my ACKS: The Dark Project or Barbarian Conqueror King settings. It is particularly fitting for a setting where Dwarves are a dying race.
The idea is this: a small human (or mostly human) town is situated in a relatively steep valley. It is ruled by a human noble who has a small keep at the top end of the valley. The town makes its living from providing some services to the surrounding mountain villages (mostly raising sheep and goats), as well as some iron (or gold?) mining in an old mine not far from the keep and some trade. Naturally, the town also has a small Thieves’ Guild.
Unbeknownst to most town people, the town has been built on the ruins of an old Dwarven Vault, which once lorded over a large domain, much larger than the current human ruler’s small domain. The ruins of the top level of that vault serve as the foundation of the human town; the lower levels connect to the old mine still used by the town, as well as the town’s sewers. Most humans do not know the origin of their town.
The reason the old vault was abandoned was that an Aboleth invaded its lowest depth, a flooded gold mine, and preyed upon the Dwarves. Some time after the fall of the old vault, the Aboleth entered torpor, and apart from some creepy legends and some ruined surface and near-surface construction, all was forgotten about the vault.
Recently, the Thieves Guild, who use the sewers for the purposes, has opened up the old vault. Thieves have sneaked down its depth, and unintentionally awakened the Aboleth. Now this great beast has taken over the Thieves Guild, and plots to take over the town.
the "dungeon should be:
Level 0 - town, keep and working mine
Level 1 - sewers and cellars, infested with thieves and rats
Level 2 - upper Dwarven vault (living quarters), infested with thieves and Skum
Level 3 - middle Dwarven vault (market, manufactory, chapel and catacombs), infested with Skum and Undead
Level 4 - lowers Dwarven vault (palace and mines), infested with Skum and worse
Level 5 - Old Flooded Gold Mine, where the Aboleth lurks!
Adventure hook could probably be the PCs hired to investigate the recent sharp increase of crime in the town.
How well would this work in ACKS? I’m especially interested in how this will interact with the domain system - for example, what will happen if the PCs defeat the Aboleth and clear out the Vault? Would this be a Sinkhole of Evil?