An updated edition of the OSR adventure Shadowed Keep on the Borderlands is out in print and PDF from Raging Swan Press. The adventure is designed for first level characters and makes for a great jumping off point for any old school fantasy campaign. The 118 page B&W softcover (with PDF) is available at DriveThruRPG for $21.95 or grab just the PDF alone at the Raging Swan Press site for $13.95.
About the adventure:
Shadowed Keep on the Borderlands is designed for a group of 1st-level characters. The adventure is set in the Duchy of Ashlar, which is part of the Gloamhold campaign setting, but can easily be inserted into your own campaign world. The keep’s location—a bluff surrounded by dense woodland—is generic enough to fit any but the most atypical campaign. Similarly, the one-time ruler of the fortress is nothing but an adventurer made good and not the scion of some noble house.
The Shadowed Keep on the Borderlands is a sandbox adventure—the characters can explore the various zones of the keep in almost any order. Thus the characters will find some areas easier than others, and they may never even discover other portions of the complex (particularly locations D14 – D16). Similarly, there is no time pressure during this adventure—the characters can explore the Shadowed Keep at their leisure. If you would rather a faster-paced adventure, consider placing a rival group of (black-hearted) adventurers in the area also intent on exploring the ruins. This gives the characters an impetus to explore swiftly and potentially sets up a climactic fight with the rival adventurers somewhere in the ruins!
Once the party has cleared the keep the characters can move on to their next adventure or they can claim the fortress as their own. In this way, the keep can become the focus of an entire campaign as the characters battle to clear the surrounding woodland of enemies (or explore the deeper caverns below the keep) while repairing the shattered fortress. The obstacles to successfully completing such a task are legion. (Refer to “Further Adventures” for more details.)
Characters completely exploring the keep and defeating all its challenges should reach 4th-level by the end of the adventure