Castle Xyntillan

The Castle Xyntillan sourcebook features an adventure for levels 1–6, set across three massive floors of a complex megadungeon. The stats are compatible with various OSR systems, such as Swords and Wizardry. A separate map supplement is included.

Still hesitating? Read this review by Bryce Lynch. "This however IS the only adventure you ever need. You could run a party through this for YEARS, with more than enough information present to riff on. A perfect OD&D product, with whimsy and wonder without going off in to Funhouse territory."

The book is in English, has a hardcover, and spans 132 pages.

Castle Xyntillan is one of my personal favorites from the current OSR scene… A "spooky" castle designed as a megadungeon. "Spooky" is in quotes because it’s that stylized, humorous kind of spooky—singing skeletons in uniforms, animated statues, talking paintings, eerie wailing, stuffed monsters… The building is incredibly vast (300 locations) and packed with all sorts of traps. It’s far from just combat; there are plenty of non-lethal puzzles, weird magic items, and 60 NPCs (!). It’s obviously not "realistic," yet the game maintains an internal logic, thematic arcs, and recurring motifs that players can learn to navigate.

Megadungeons often risk becoming repetitive, where doing the same thing over and over loses its charm. I think Xyntillan successfully avoids this—the deeper, harder-to-reach areas shift thematically, the difficulty naturally scales, and at one point, the environment changes entirely, almost as if you’ve stepped into a fairy tale. The module also has several built-in "quests" that players can discover and solve, giving the game structure so it doesn't feel like aimless wandering. The evolving relationships with members of the Malévol family, who have their own grudges and schemes, add further dynamics.

In short, Xyntillan is a brilliant example of level design for an open, sandbox game. You can go anywhere and do anything… and no matter where you go or what you do, an interesting story thread will emerge. Different locations are interconnected, referencing and influencing one another, while various elements or "tasks" encourage further exploration…

From a review by Jiří Petrů on Rpgforum.cz