The Library at Celaeno Map Expansion contains a new map with two figures, the Librarian and the Custodian. This map is inside the cyclopean alien facility in the Hyades, renowned in Lovecraft lore. This map includes Special Collections, where the first player to build a Gate can seize amazing new powers in the form of extra spellbooks. But beware! If you lose control of your Special Collection, your new spellbook becomes overdue, and the terrifying Librarian menaces you.
The Custodian cleans up chambers by moving units in the Area to another Area termed the Oubliette. Over the course of the game, this Oubliette tends to get filled with units. Sometimes fights break out.
The Librarian can only be activated if a player has an overdue Book, in which case it can wreak some real damage. Fortunately, you can mitigate the damage by returning the Book, though not necessarily eliminate all threat.
The Library at Celaeno introduces a new mechanism in Cthulhu Wars: Silence tokens. These are used to trigger certain special actions including moving the Custodian, Librarian, and triggering some of the special Library books on this map.