This is the second story arc in the Darrowshire Campaign Setting.

This story arc begins with the party's exodus from Darrowshire in pursuit of a solution to the Crowd Problem (and possibly preservation of their lives), and is in three [check this] parts: The Exodus, The Arrival and Exploration, and The Entrance to the Temple and the Opening of the Portal.  During The Exodus, the party is running from Darrowshire, seeking the Keep on the Borderlands as basecamp for their search for the ancient Void temple.  Once there, they begin the Arrival and Exploration phase, where they meet everyone in the Keep and begin to explore the surrounding region (both inside the Caves of Chaos and without, as there is more to the surrounding countryside than just the Caves).  Finally, when they find the correct cave in the Caves of Chaos and enter it, they begin The Entrance to the Temple and the Opening of the Portal phase.  Following their (accidental) opening of the Void Portal, they begin the third story arc, "The Poral and the Mists" [link?]

This story arc relies heavily upon the classic module b2 the keep on the borderlands [format and link].  If you do not have access to this module (it can be purchased easily online), simply make up the missing details of the Keep, using the "rules of the keep" [edit] document, create a surrounding countryside, and generate a valley full of caves and lairs of monsters, with a final temple to contain the Void Portal.  It is by no means necessary to purchase the module, but it will save time and effort for a DM who does not insist on creating every last piece of material from scratch.  I only used it because I wanted an excuse to use my favorite module, and because it is a well done piece of work.  A few of the adventures in the Exodus phase mention various things from published material.  The same thing applies to them.  I used them because they were good works, and they fit into the campaign setting well.  You are certainly not required to do the same; I merely include them here for convenience and trueness to the original version of the campaign setting.