Dungeons & Dragons Monte Cook: Arcana of the Ancients: Where the Machines Wait

This 96-page adventure is, in essence, a massive dungeon in the form of an ancient megastructure called, in-game, the Grave of the Machines. It consists of what amount to six levels, each of which with its own threats, dangers, and subplot opportunities.

One of the levels is inside a ruined lost city under a dome. Another is essentially one vast mechanism inter-penetrated by maintenance tubes and inhabited by sapient machines. Another is a vertical, slowly rotating wheel-like structure. Another is half-drowned, filled with breathable superfluid. And in the deepest level—the Creche—something dangerous is kept. If PCs can get in, they’ll  find  . . .  well, maybe that’s saying too much.

PCs can dip in for straight-up exploration and ruin-crawling, returning to the surface periodically to sell their salvage for gold. In so doing (or, if you prefer, as the main driver of the adventure) they may also accept specific acquisition requests—which may then lead the PCs into a deeper, overarching plotline. Perhaps the patron knows about something specific down there. What is it, and why does he want it? Can he be trusted, and is it safe to bring his target, buried for so many aeons, to the surface?

Where the Machines Wait also has about a dozen new items and a similar number of new creatures—including one that’s a new PC-playable species.

This is a 5e title, but for Cypher System fans there’s an appendix making it easy to use the adventure for the Cypher System.