You Used to Scrawl Me In Your Fel Tome

After digging around the instance for a good hour or two on normal, I managed to find all six notes hidden in the instance, and took some screencaps to point them out:

Torn Page:
Found in the Chamber of War Room immediately after the Amalgam of Souls fight, on a desk by the southern part of the room.

Worn-Edged Page:
Found in the Grand Hall, to the left of the broken staircase, by the bookshelves.

Dog-Eared Page:
Found in the Grand Hall, it's in the hallway connecting to the stairwell that takes you to Illysanna Ravencrest, tucked in the back on a desk.

Singed Page:
Found in Rookshold, the room filled with Wyrmtongue Tricker, on a table by three bookshelves and two weapon racks.

Ink-Splattered Page:
Found in Rook's Rise, in the small round room connected to the stairs leading to Lord Ravencrest's Chamber after defeating Smashspite the Hateful.

Hastily-Scrawled Page:
Found in Lord Ravencrest's Chamber on the desk, at the end of the instance.

These spawn on Normal, Heroic, and Mythic difficulty, and you'll only get one per run, making this achievement a six-run minimum.

Day 1:I found 5 tomes in 6 runs, this achivments seems easier than I tought it would be.
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Day 9: The elusive Singed Page did not spawn yet. I will keep trying.
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Day 283: I've been trapped in this place for month... maybe even years. Spider and goblins tried to eat me, I cannot tell what is real or what is a figment of my imagination, but I must persevere, my survival depends on it.

Easy but extremely Repetitive Solo for Level 120 and Beyond...

1. Normal Difficulty.

2. There are 6 locations for the letters you need to read, and only one will spawn per instance run. As a result, this can virtually be completed in a minimum of six runs. You can reset the instance to get a fresh letter location, but sometimes it will be in the same location, when that happens leave instance and reset again.

3. Locations are in order of start to end of instance. Watch the video to get the visual of the locations:

https://www.youtube.com/watch?v=9SwwuBuACwY&feature=youtu.be

Library Desk - Torn Page (On the right side desk in the library you enter after killing the first boss.)
Bookcase in Grand Hall - Worn-Edged (On the left side of the Grand Hall where the commander and his archers spawn before second boss)
Desk to the Right of Grand Hall - Dog eared Page (Once you kill the commander and his archers, the gate opens, this desk is right around the corner before second boss)
Wrymtongue Hallway Desk- Singed Page (On the desk, in the hallway with the Wyrmtongue Demons on the desk after the second boss)
Pedestal after stairs - Ink Splattered Page (just before stairs leading up to Lord Ravencrest's Chambers and the Final Boss, third boss must be killed, and then the gate opens)
Lord Ravencrest's Desk - Hastily-Scrawled Page (just before Final Boss)

4. So, run, read, and reset instance, until you have read all six diary entries.

5. Extremely boring and repetitive. This took me 14 runs. I have heard nightmare stories of 50+ and some as low as 7. It is entirely Random.

6. ?

7. Profit. Achievement Completed.