Mysancta was a dedicated student of the mysteries of the Abyss, and prone to tedious harangues about the masteries of darkness possible only to those who forsake the flesh. He spent as much time as possible in shadow form, extruding semi-tangible paws to push around a silver frame on which servants draped cardinal’s robes. The spiraling wires supporting the cardinal’s glass crown chimed softly as a shadow paw pushed the headpiece forward in imitation of a human’s bending gaze.
He is the mentor of the young Lasombra named Skiapena.
Page 18 of the Clan Lasombra Trilogy Book 1: Shards says Tresaric remembered Mysancta as having once been a middle-aged woman. It's worth noting that page 207 expresses confusion around the subject of Mysanctas gender saying: "He’d been waiting all evening to do a fitting for Cardinal Mysancta, only to have her (or him, or it, as might be) cancel at the last minute".
However, page 22 of the Clan Lasombra Trilogy Book 3: Sacrifices refers to Mysancta as follows "Mysancta spoke for the first time, from within his robes".
It's not clear whether Mysancta is a transexual or if Tresaric's memories are unreliable.