Written in the Ninth Age, the Metalogicon is one of the great works of the central Thyrnessan period. It is a modern interpolation of a more ancient work which collates and analyses diverse philosophies from Aellon and Miles but focusing mostly on the application of logic itself to various philosophical schools. The main elements come from Avaridus' codification of logical systems, but the work itself was authored by a Quilian monk of the city of Miles named Theolendus.
Widely considered to be sacrilegious in its contestation of many details of the so-called revealed mysteries of Orijen and Aeldus (in the record of Hierian faith known as the Scroll of Law), Theolendus Gravus was eventually expelled from his order and forced to live in exile in a land more accepting of his analysis—namely, High Aellon itself. He spent the rest of his days living in Chimeros and dwelling amongst the books rescued from the fall of Byblos.
While not a magical manual (like the Tehkne manuscripts of the Old Empire), the intense study of the Metalogicon can provide one with benefits beyond normal reading. Indeed, anyone who takes the time to read a copy of this revered book and study it over the course of three months can purchase (at no slot cost) the new proficiency Logic (Int -3) which, when checked against, allows the character to make one test or proficiency check as though their wisdom were actually 2 points higher.