Codex Lahyum is a magical treatise and tome written by Kumono during the late Third Age. It combined what he knew about Necromancy with considerable information of magical forms of Reincarnation. Only three original copies of the book were ever made, though numerous mass-market "print" copies were also created.
Kumono cited the Mehi Codex and numerous other works (most long lost after his time). He provided one of the best technical explanations for the commonly used process, as well as reproducing several several of the necessary spells and rituals. His work was incomplete, and could not be used to complete an actual reincarnation. In the book, Kumono discussed three forms: Necromanic litchdom, classic reincarnation as used during the Mage Wars; and a third, unnamed form only speculated on.
Status of Codex
Authorities are split as to the purpose of the work. Many hold that Kumono was attempting to reincarnate himself; an act explicitly forbidden by the office of Pendragon. However, his contemporaries did not hold this view, and much evidence indicates that he had little in mind beyond centralizing and cataloging as much information on the process as he could. Lal had unprecedented access to living Necromancers in his day, and the ability to gather considerable information from them that would not have been available to anyone else. His own notes state outright that his only goal was to "unlock the secrets" of reincarnation.