Mysterious chronicle (part 6) 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 1324 of the Fourth Age. Bilrach's digging has led to a warmer area, likely referring to the switch between the Frozen floors and the Abandoned 1 theme. He believes this area will make suitable habitation for his followers, and that they should fear him.
Year 1324 of the 4th Age:
The area I've broken into below is beginning to exude more heat. It might even be suitable for my minions to dwell here, to more efficiently serve my cause. Those who refuse to move here out of fear of my power, I will just force or kill. They dare not to question my rule. They dare not stand up to a Mahjarrat. They dare not question me, Bilrach, their master.Zamorak be praised!