Mysterious chronicle (part 9) is a book found only in Daemonheim. It may appear in front of the dungeon-ending ladder after killing the boss monster.
It was written in the year 1424 of the Fourth Age. Bilrach recalls that he just passed the two-century mark into his descent. He intends to use the great power at the bottom to control kingdoms, and that he must beat those who also seek this power.
Year 1424 of the 4th Age:
If memory serves, I've passed the two-century mark of tunneling into this place. I feel the pull of the pour below. If I reach the bottom, great reward will be mine and the world will burst open as I dominate the kingdoms of this frail world. Enough, I must return to my work. I cannot guarantee that I am the only one seeking this, and must beat any who also seek it, as if they could stand up to me.Zamorak be praised!