A grate in the floor is the internal entrance to the library ( 4, -26, -131 ) /waypoint 4, -26, -131 down on the second level of the zone. The external entrance to the library is here: ( -24801, -40, -234 ) /waypoint -24801, -40, -234. A crushed librarian is specifically at ( -107, -32, -156 ) /waypoint -107.21, -32, -155.59. Also, Qelinatias the Scion of Pain 24^^^* and a named briar spawn in the same room as the internal library entrance.
Click the sarcophagus just to your right as you enter. This will spawn about eight restless stormlords (25 and 26 Heroic ^^^).
Kill each stormlord as you progress forward through the tomb. After each kill, close the corresponding sarcophagus.
You will have to run back and forth closing ones that you had already closed.
After you kill the last restless stormlord and close its sarcophagus Lord Chesgard (30^^^) and all of the previous stormlords will spawn (be sure you are at the opposite end of the zone-in point against the wall. Close the last one near the opposite end or get caught in the respawn). Repeat the process back towards the zone-in and Lord Chesguard.