Journal of Reardon
The Journal of Reardon is said to be the diary of Reardon a man believed to have turned his back on The War and on magic. It i said he was subsequently killed for doing so, although his teachings lived on through his writings.
It is said that years after his death a person known only as The Student found this journal and began following it's teachings. They then went on to pass these teachings onto others eventually growing into the order known as The Watchdogs.
No one seems to know where this book is now, in the many centuries since it's writing and rediscovery, its whereabouts have long since been lost to time.
While no significant boon is known to be bestowed upon anyone possessing it, the historical and near-religious value of it would be incalculable.