Book of Imperial Precedent
This is the text of the words of the emperors through the history of the empire. All law within the Empire is based upon it and it is continually updated as new emperors add new rulings. All the rulings of the emperor are seen as divine and so must be obeyed. If the Empire has a holy book this would be the closest to it. Order of Law has the largest number of copies of this as street Justices have a copy on them at all times (part of their official regaila with the heavy gold chain that it is attached to. This might partly explain why so many street Justices are dwarves) The tomb is of signiificant size and weight currently being around 15 inches high, 11 inches wide and 9 inches thick.