Fabled Compendiums

Sof Sator contains more mysteries than most imagine, and those who uncover these secrets tend to find yet further mysteries hidden beneath them. Several of Sof Sator's most mythic figures are researchers, seekers, and explorers who have dared to uncover and record knowledge that is forbidden, rare, and dangerous. The tomes, correspondences, and records of these figures have become treasures themselves, sought after by those who would imitate these mythic figures, or those who desire the magic that they uncovered. Many treasure-seekers or purveyors of relics claim to have such Fabled Compendiums in their collections, but very few are authentic, and anyone lucky enough to come into possession of such an authentic item tends to meet an unfortunate fate soon after.
Of these many mythic researchers, four are usually considered the core of the fabled canon, and their bodies of work are sought after by collectors all over the continent.

The Ebon Aquil's Lost Libraries

Though the myth uses the Jei-Satorian word Aquil to name him, the Ebon Aquil seems to be one of the last surviving members of the Vedrfol species. Having met his end as recently as 820CR, he seems to outlived the rest of his species by almost 1600 years. This is far from unbelievable; according to what few reliable sources of information date back that far, the Vedrfol lifespan was meant to last several millenia. How and why he was spared from extinction for so long is not part of the myth.
What matters is that, owing to the secretive nature of his species, the Ebon Aquil spent his extra millennia-and-a-half of life preserving the many texts of the civilization of Jeimr and concealing them in secret libraries throughout Sof Sator. Legends of these libraries place them on mountainsides or in deep valleys, places impossible to reach without flight and impossible to see from the outside. It's a common subject among Sof Sator's mountaineers, and those lost to the mountains are sometimes said to have fallen into a library.

Known Artifacts:
Rime, Salt, and Dim Fathom, circa 1500 U.C.
Record incomplete.

The Alchemic Psychopomp's Correspondences

Legends vary on the origins of the Alchemic Psychopomp, though most place her at the intersection of Arin and Ossea around the time of Revan's campaign of extermination. Her mythic ability to interrogate the spirits of the recently deceased does resemble Arinite Soul-Binding practices, though not perfectly. Whatever she once was, however, she has deviated far enough from her origins to become a figure of myth instead of simply history. Discovered correspondences span 800 CR to 1000 CR and do not hint at any weakness, illness, or demise, so most myths consider her to be still alive and active, though no correspondences have been found dating more recently than the turn of the millenium.
The Psychopomp's correspondences most commonly describe encounters with the dead and the revelations they share, though she has also gained knowledge from the living and from her own waking actions.
Known Artifacts:
An Encounter With the Ebon Aquil
A Theory regarding the Green Voice
Record incomplete.

Vali Neyr's Compendium of Secrets

One of the compendiums more grounded in history than myth, Vali Neyr's only mythic quality was his love for exploration and skill at investigation. A Tercaelo from the Rhyqirja Mountains -- perhaps one of the only Tercaelo to willingly leave the peaks in this century -- Vali Neyr drafted tomes full of knowledge about history, governance, and magic, all of which he carried with him as he traveled across Sof Sator. During his life, many influential leaders and academics considered him both a curiosity and intellectual peer, and as a result Vali Neyr was invited to symposiums and salons where he could speak to persons possessed uncommon and specialized knowledge. It's recorded that Vali Neyr was particularly skilled at convincing peope to share knowledge, that he remembered and recroded many of these conversations, and that he would not limit himself to learning only what was permitted. In 1031 CR, Vali Neyr was formally banished from the Cradsoun Hegemony for stealing state secrets from secure archives.
Vali Neyr was driven by a peculiar morality that secrets should not exist and that all knowledge should be freely available. He intended to widely publish his compendiums, with all of the rare magic and state secrets they contained. However, the last known contact with Vali Neyr was in Pharaul in the year 1052 CR, where he was attending a meeting of the governing forum. Since then, there are no reliable records of any sightings or communication with him. He seems to have disappeared with the entirety of his compendiums, though tales now abound of his tomes turning up in various places throughout Sof Sator.
Known Artifacts:
What Can Be Known of Jack o'Shadows
The Secretive but Very Real Alchemic Psychopomp
Record incomplete.

Jack o'Shadow's Cursed Anthologies

A figure as much of ghost stories as of myth, tales tell of treasure-hunters who -- while seeking Fabled Compendiums full of ancient knowledge and magic -- instead find a cursed book drafted by Jack o'Shadows. These tomes are scattered throughout Sof Sator with the stated goal of dooming anyone who picks them up. The very first lines of every book explain that by opening and reading from it, one has cursed themselves to die, and threatens an even worse fate if the reader tries to damage the book in any way, or if they make transcriptions of the books contents. The book then invites the reader to continue to read, as the curse won't get any worse from then on.
Much to the anxiety of treasure-hunters across Sof Sator, these books out of all others are proven to exist and carry potent magics. Tomes written by Jack o'Shadows reside, sealed in glass safes that protect against the curses on the books. Their contents, mostly unread, are thought to be stories of monstrosity, horrible magics, and unspeakable crimes.
Known Artifacts:
The Bloodletter's Cult of Redfall Reach
Blood, as Reagent
Vali Neyr, Fool of Hodm
Record incomplete.