Silver – May be why Arimaspians considered Vale Sanogroa holy? Associated with Nassur, the Serpent?
Berossus – "One-Eyed Slayers of Griffins, Speakers of Forbidden Words" – must mean Arimaspians
Achilles – promise of strength, immortality
Anca's Scribbles
The quest thread it belongs to
The game files this document under one quest code, and that code covers all 2 of these journal entries. It belongs to the thread; the data does not say which entry.