Grand Cleric Callista held the position of Grand Cleric of Orlais from Val Royeaux circa 9:22 Dragon. As second only to the Divine within the Orlesian Chantry hierarchy, she served as Divine Beatrix III's most trusted advisor, presiding over numerous regional temples. Her duties included participation in the Grand Consensus to elect a new Divine following Beatrix's passing.

Callista initially presented public support for the Seekers of Truth, praising Cassandra Pentaghast for slaying a drake at the Grand Cathedral. However, she later commanded templars, not Seekers, to apprehend Cassandra after the disappearance of a young elf named Avexis. This act masked Callista's secret alliance with Knight-Commander Martel and Frenic, a blood mage cult leader. Together, they conspired to assassinate Divine Beatrix III and fellow Grand Clerics during the Ten Year Gathering, intending to secure Callista's elevation to Divine.

When the assassination plot failed, a severely wounded Callista stumbled towards Frenic seeking help. Frenic responded by fatally stabbing her with his staff, declaring he had merely manipulated her ambition for his own purposes. Her death revealed her role as a pawn. Within official Chantry records and public discourse, she was referenced solely by her titles – "Grand Cleric of Orlais" or "Your Grace" – never by her given name.