The Psijic Order is an ancient, magic-wielding order. From it, the Mages Guild would later develop. The Psijic Order is believed to have originated in the Summerset Isles. They are said to have developed Mysticism long before there was a name for it. When the Altmer began to settle more permanently on the Summerset Isles from their ancient home of Aldmeris, their culture began to change.They no longer worshipped the ancestor spirits, but several of those spirits such as Auriel, Trinimac, Syrabane, and Phynaster became gods that the Altmer worshipped instead.Many elders, who called themselves the Psijics, rebelled against this trend, as they were the keepers of the Old Ways.They used their mystical powers to settle in Artaeum, away from the "corruption of their society." They frequently returned to the Summerset Isles to offer advice and guidance, however. Mannimarco, was a student of the phijics, before he turned to necromancy. As far as I know, the thalmor is afraid of the phijic order. But in all honesty, who isn't?