Prayerbook of the Roundtable HoldLandmark's assassins. Can be given to a learned cleric to gain access to the following incantations: - Assassin's Approach - Darkness

Can be found behind the second Imp Statue door in Roundtable HoldLandmark, the first door will require one Key to open, and the second door behind the first requires two keys to open. So you will need three keys total to unlock this.