In Lords of the Fallen, the Book of Sin is a quest item that is needed to complete the questline of Exacter Dunmire. His whole questline is for you to find multiple items related to obtaining knowledge. Book of Sin is one of these numerous items and is found in the Pilgrim’s Perch while in the Umbral realm.
Lords of the Fallen Book of Sin location
To get the Book of Sin, you’ll need to go to Pilgrim’s Perch and find the Vestige of Blind Agatha. Start from the Vestige of blind Agatha and go into the tunnel on the right.
Stay by the left wall until you reach a door. Cross it and then turn right, which will lead you outside. Jump on the platform to get to the next side.
Cross the connected narrow path where the enemy with the spiky headgear in Lords of the Fallen is and go down the ladder.
Just on your right would be another ladder, but don’t take it yet, as you’ll fall halfway through. Transform into the Umbral realm and then go down. Cross the platform and go towards the far ladder to climb up.
Turn left and climb up again. On this platform, you’ll see a bone bridge in Lords of the Fallen. Be careful while crossing it, as there is an enemy on the platform it is connected to. Transform into the real world, as it will clear up the area now. Turn and run towards the right until you reach the bell.
Go down two ladders, and you’ll encounter a lot of enemies, so be prepared. Transform into the Umbral realm again and go down the bone bridge onto another platform. From here, go towards the platform directly under the one where you fought a lot of enemies.
Here, soulflay the Umbral stigma/node in the middle. This will give you the Book of Sin in Lords of the Fallen.
Where to use the Book of Sin
The Book of Sin is used to complete a part of Exacter Dunmire’s questline. Travel to Skyrest and find him in the study room. Talk to him, and you’ll get the option of giving him the Book of Sin. If you do, he’ll just be happy that he got some proof of the practices done by Hallowed Sentinels.
You can also choose not to hand it over and continue with your game. This is not a requested item but a book that can help his research. It won’t affect you either way. However, it is better to give the book of Sin in Lords of the Fallen to him as keeping it would be of no use to you at all.