Mysterious chronicle (part 11)

Mysterious chronicle (part 11) is a book found only in Daemonheim. It may appear in front of the dungeon-ending ladder after killing the boss monster.

Written in the year 1464 of the Fourth Age. Bilrach explains his sanity. He says he is as clear of mind as he was when he started the descent. He realises his methods and the nature of this place may seem random, but that he is yet to use the more dangerous and unstable side of his power. His sanity is unwavering; he says his hearing of whispers from the earth below is not a sign of his mind breaking, it just confirms that he's getting closer. He asks if he should be concerned that the whispers try to guide him.

The whispers seem to have some level of influence over Bilrach; He denies his insanity, but he does consider it (or else he would not have made note of it). This may be a reference to Edgar Allen Poe's Tell-Tale Heart.

Transcript
Year 1464 of the 4th Age:

I'm as clear of mind as the day I started this descent. My methods and the nature of this place may seem random, but I've yet to use the more dangerous and unstable side of my power. My sanity is unwavering; hearing whispers from the earth below is not a sign of my mind breaking, it merely confirms I am getting closer and should continue down. Should I be concerned that the whispers try to guide me?

Zamorak guide me!