The other thread doesn't get updated, plus I think pictures would be useful. I'll keep this one updated as much as I can:
Steps:
1: Pull the lever in the illusion room that changes for everyone. Also you need to split up before this room or step 3 will be impossible.
2: After this room, go up the stairs. Just before the drop down, look to your left and there should be a brick sticking out of the wall. Interact with it.
3: Now, go to where you find the 2nd tome. The door there will now open, revealing a statue. This means your team will have to split up, since there is no way to go back after the illusory room.
4: Place the statue on the white markings that are just before the appearing bridge.
5: After the room reverts back to normal, go back to the statue and you will hear a noise. Besides the statue, a painting will have appeared.
6: finish the stage.
7: Start the stage again, do everything again to get the statue, and put it in the place you see in the painting ( which is in the large hall the first tome is in, top floor). This will trigger a flash of light, turning the room misty and making 4 skulls appear at the base of the statue.
clues for current step: "knowledge is king"
When placing the statue in the library, books will spawn which can only be viewed by certain characters. After standing on these books for 10 seconds, a light effect will appear and one of the skulls will light up.
If you find the next step or if I missed something, please send me a message
http://steamcommunity.com/sharedfile.../?id=973128579 great guide that has some interesting speculations about the next step