The Bronze Vault (Patreon)

The Bronze Vault is a small, multi-level complex cut into the Jappa Slopes and connected to one of the small cavers that dot the hillsides. Once connected to a small watchtower that was built too close to the edge, getting into the complex typically means climbing to the ruins as the door between the cave and the complex is locked, barred, and now rusted shut.

In-game, the complex fills the role of any classic “dungeon in the wilderness” setting – a place where civilization once held sway but is now home to monsters hiding in the roots of our achievements. In the grand tradition of the Moldvay Basic D&D set, this is where hobgoblins would hide their prisoners captured from the nearby town; perhaps home to a small cult that cannot worship publicly in civilized areas; or the destination for a treasure map that the party found in a previous adventure.

Personally, I like the treasure map angle – making the secret chamber in section B right by the entrance the treasure room, but with the map showing how to get there from the cave entrance instead of the upper entrance.

https://rpgcharacters.wordpress.com/2018/09/13/the-bronze-vault/