From the publisher's website: A group of vile humanoids has taken over an old, ruined keep within a day's walk of the nearest town. Local leaders greet this news with alarm, for they don't wish to see a stronghold for evil humanoids so close to their settlement. So they offer a deal to your group of adventurers: Root out the humanoids and you can have the keep as your own base of operations. Base of Operations, a short adventure intended for four 5th-level characters, is a site-based scenario designed to be either very brief (one or two sessions) or part of an ongoing campaign. Player characters have the opportunity to save a town from a horrible fate, rid the world of a vile necromancer, and find a little wealth in the meantime. Or, if the DM wishes, the adventure allows for player characters to set themselves up in their own "base of operations" and become permanent members of a community.