Awakening this new army costs 10,000 gold and 800 Jars.
In the Mortuary Cult, “A New Dynasty” gives you +1 to the number of armies you can field (Army Capacity). You need Canopic Jars! Hereafter I will just call them Jars. Send a Hero to discover the roaming book armies (the Book of Nagash map will show you where they are, but you have to encounter them for them to show up in your diplomacy screen) and then Declare War on them so that they come to you to attack you so you can kill them and take their Books of Nagash.