Mysterious chronicle (part 12) 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 year 1505 of the Fourth Age. Bilrach expresses his frustration at his slow progress, but asserts that he must focus on continuing, as there is only one thing powerful enough to emit the power across planes of existence.
Year 1505 of the 4th Age:
Progress is frustratingly slow, as of late, but it is progress at least. I'm nearing the end with every day and I must retain my focus, my drive. I know what dwells at the bottom - there is only one thing powerful enough that can emanate power across planes of existence. I must be right.Zamorak be praised!