By Arthur-Trevor D.M. Lasher, for The Southron Republic
Manichaens are specially-designed Revenants, modified by Progenitor procedures and Tzimisce Vicissitude. They are born tabula rasa, with no personality engrams or even much dura matter, outside of a residual medulla and brain stem. An individual's brain is surgically placed inside the Manichaen body and molded to a perfect fit and it is only then that the Revenant's true nature comes to fore.
The transplantee's brain triggers the Revenant body, causing its latent Vicissitude to shape itself to conform to the brain's self-image. This image may not necessarily be identical to the original template. Often it is an idealised image. The finger and retinal prints, however, remain the same as the template. The Manichaen now is a stirling near-carbon copy of the transplantee's original body...with a twist. For now the template can live to several centuries of age and benefits from the body's low-level Vicissitude (limited to Flesh and Bonecrafting to him or herself, only).
Mages who transplant their brains into Manichaen bodies find an additional benefit: the full use of True Magicks. Being alive and not undead, the Manichaen's Avatar is identical (or so they think...) to the template's. Whether this is accomplished through transplantation or some kind of 'soul cloning' is unknown, though it is certain that the Tzimisce hold the key to this process and it is the culmination of several centuries of experimentation along the Path of Death and the Soul.