Book 21: The Magic of Ancient Judges, by Argus of Jerbiton (Communication +3, Wisdom of Athena Mastery 7, Oath of Truth Master 10, The Will of Alatheia Mastery 8)
Order of Hermes Lore Tractatus (Quality 9)
Code of Hermes Tractatus (Quality 9)
Wisdom of Athena Summa (Level 3, Quality 9)
Oath of Truth Summa (Level 5, Quality 9)
The Will of Alatheia Summa (Level 4, Quality 9)
Argus of Jerbiton was a Mercurian mage who lived and died about two centuries ago. In his time, he was recognized as the foremost expert in Fenicil's rituals. His record as a Quaesitor was impressive, and his judgement in legal cases was universally respected. So his odd, possibly Twilight-induced, personal habits were mostly ignored. The historical record contains his accomplishments, and does not mention how he used to carry dead animals everywhere.
This huge, thick, heavy book is considered the authoritative text on the spells contained within. It speaks of their histories, how they were discovered by the Order, the situations in which they are useful, the legal rulings surrounding their use, and notable stories of their use. But mostly it explains how best to cast them. It's clear, straightforward, and extremely detailed.
In places, sections of text have been blacked out. It's generally assumed that this was done to contain dangerous or politically sensitive information, but in fact it was an attempt to preserve Argus's dignity. His apprentice didn't want his memory besmirched by a bit of deranged rambling.
The Magic of Ancient Judges is written in Latin. The only known copy is in Fenicil's library at Magvillus. Any Guernicus mage who visits is welcome to study it, but members of other Houses are strictly forbidden even to open it.