Once you have acquired all three, click the lever behind Stalis Ra'Dal, at ( 923, -45, 355 ) Copy/waypoint 923, -45, 355.
Click on the clay golem NPC Re'Adon and you will automatically give him the books.
Stick close to Re'Adon as he slowly makes his was past the secret walls.
Once you're inside the library, continue down all the steps and click the book titled, "Passage to Oblivion", at ( 929, -66, 556 ) Copy/waypoint 929, -66, 556.
Silren will spawn at ( 957, -77, 613 ) Copy/waypoint 957, -77, 613.