The Vault Is a City, Not a Level

Vault of the Drow is where a lot of tables finally admit they are not in a dungeon anymore.

Erelhei-Cinlu is streets, houses, temples, rivalries, and a market that will buy what the surface pretends not to sell. The caves on the way down were the tutorial. The vault is a domain with a ceiling. Factions have payroll. Nobles have estates. The priestesses are not a boss roster. They are government.

5E wants this as a set-piece underdark tour. Cool architecture, a fight in a plaza, extract. ACKS looks at the same pages and sees reaction rolls with consequences that outlive the session. You can bribe, ally, offend, or vanish. You cannot “clear” a city unless you are willing to become its problem. Henchmen matter here more than in any hallway. So do disguises, syndicates, and the simple question of where you sleep without waking up owned.

This is the adult dungeon. Not harder rooms. A society that was here before you and will be here after the party is a rumor.

You can still kick in a noble’s door and die like tourists.

Or you can play the ACKS version: the vault is a hex crawl with manners, and every coin you spend down there buys you a name the surface world will someday wish it had never heard.