The locations of all entries are in Cadash Thaig. As you pick them up, you will receive Codex entry: Letters from the Past.
- Worn Note: In a chest at the second magical vortex, near the first light.
- Worn Journal: Pile of bones between the fourth and fifth vortexes.
- Torn Letter: Pile of bones south of the sixth vortex.
- Scrap of Paper: Hanging on a spike to the left coming off the very last bridge.
You will gain experience points and the "A Time of Wood And Stone" achievement.