@Bigdoser; So far, this what we know about the Mortalitasi.
From WoT, "Nevarrans believe that when a soul crosses the Fade at death, it displaces a Fade spirit. Caspar Pentaghast's personal adviser, a Tevinter mage named Vitus Fabria, founded the Mortalitasi order of mages and first preached the idea. The Mortalitasi believe mummifying corpses to keep them intact provides a safe host for the displaced Fade spirits.
The mummified corpses are placed in massive, elaborate tomb, and the grandest of these come complete with gardens, bathhouses, and ballrooms. Wealthy Nevarrans begin construction on their own tombs while young, and add to them as they grow older. Outside of Nevarra City stands the Grand Necropolis. It appears almost as a city in itself, complete with mansions and great palaces, although it is utterly silent and kept only for the dead. It is common for nobles to take Mortalitasi adviser, and rumors persist of noble involvement in secret necromantic cults. Outside of Nevarra, inflated stories of ancestor worship and obsession with the dead have become Nevarran stereotypes."
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"In Nevarra mages have more power than those in most Chantry-controlled nations. They are well organized, wealthy, and hold political sway. Nevarran mages push the boundaries of what magic can do and are arguably the most well schooled mages outside Tevinter. Among the special aspects of magic practice in Nevarra is the secretive Mortalitasi order. These mages are experts in the art of mummification, a burial practice unique to Nevarran culture. The order studies death extensively, and its members are known to experiment with necromancy. Members of the order rarely leave Nevarra. While they are well respected within the kingdom, mages outside the nation's borders fear them. Propaganda perpetuates the belief in some that the Mortalitasi are actually a death cult who carry out macbre rituals in the catacombs of their Grand Necropolis."
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"My tenure as ambassador to the Nevarran court began, appropriately enough, with a death. I arrived to find my predecessor and intended mentor, Sifas Carrenter, had died in his sleep. Not unexpecetd, given his age. Instead of a cremation, the Mortalitasi were summoned for him, those gray-robed mages who seem to be everywhere in the palace. I was warned of the Mortalitasi in Starkhaven. Some cautioned me about their political prowess, learned from sitting at the feet of kings for generations. Others talked about the Mortalitasi like they were ghoulish surgeons in leather aprons, exhuming bodies by moonlight in their Grand Necropolis. The Mortalitasi who spoke to me was a polite, tawny-haired woman who smelled strongly of soap. She explained that Carrenter had earned the honor of being preserved and interred in the Necropolis. It seems a barbaric practice, but I knew that demanding a cremation would have made me - and more importantly, Starkhaven - lose face in Nevarra. Instead, my thanks seemed to please her. She described some of their rites. Though she wouldn't speak of the greater mysteries, even a glimpse into their arts put my hair on end. But I held my peace. The Mortalitasi are linked to the throne by blood. If I die in my office, like Carrenter, my body will be in their hands. In a land where death and politics are intertwined, one should be polite."
-- Galen Vedas, Starkhaven ambassador to Nevarra, 9:6 Dragon.