Rift Quest:Greenscale's Prison  

The Book of the God Prison can be found at (832, 696) inside of King's Breach. When you loot it Rydremac the Librarian will spawn and have six Living Books attack you. Slay them and follow Rydremac down the hill, taking care to slay the three patrols here.

Rydremac is a level 35 elite mage but seeing as you're in a dungeon already, you likely have a group. He should be a push over.