In 375 LE, eldritch giant raiders went aboard the ghost ship Halatrax. On this vessel they battled undead and other guardians left aboard since the Creation War. Before being forced to leave by these guardians they plundered a chamber of relics, books, scrolls, and ornate jewelry. The scrolls filled two trunks and contained writings of Maen Grirngrim. They discuss the workings of necromancy like optimal times of casting (c.f. Shade of Darkness, Zenith of Darkness), undead creations and which ones are best for what purposes, and a number of necromancy spells. One of the more powerful spells is trap the soul and how to use it in weapons.
The Scrolls of Maen led to the development of a school of necromancy called Maen Saetild and to the birth of the order Khaa'khas - an order for those taking Maen Grirngrim's teachings to the extreme.