Libellus Sanguinis: Thieves in the Night is the fourth in a series of sourcebooks that details the clans of Vampire: The Dark Ages. The Libellus Sanguinis books are similar to the popular Clanbooks, but each presents three clans in one! Volume Four investigates the deadly Assamites, the shadowy Followers of Set and the wild Gangrel.
- Full coverage of the three clans for the Dark Ages: The Assamites, Followers of Set and Gangrel;
- Information on the lands of the Middle-East;
- New Discipline Powers, Merits and Flaws, and Thaumaturgy abilities specific to the three clans;
- Hidden truths and secret plans of the clans most alien to the European princes.