Pontiff Sulyvahn is a boss character in the video game Dark Souls III.
In his younger days as a sorcerer, Sulyvahn discovered the undying flame of the ancient Profaned Capital. The flame gave Sulyvahn a newfound ambition to conquer the Boreal Valley, which the Profaned Flame was situated under, taking upon a greatsword bearing a flame similar to the Profaned Flame's. Upon fulfilling his goal, he formed his Outrider Knights to enforce his rule, even forcing his compeers to wear a ring that, should they ever question his ideals, would drive them mad with visions of battle unending and send them afar from the Boreal Valley in said madness. He turned all inhabitants of Irithyll and the Profaned Capital into slaves, soldiers, or beasts. He also gave his Fire Witches too much of the Profaned Flame's power, knowing it will drive them mad and turn them into mindless servants.
Sulyvahn would eventually institute worship of Aldrich, Devourer of Gods, into the city of Irithyll, taking the title of Pontiff upon it's formation. The Church of the Deep would regularly grant Aldritch sacrifices, to sate his insatiable hunger. Sulyvahn decided to further his grip over the Boreal Valley and sent Aldritch to devour Gwyndolin, the last of the gods in the old Anor Londo, and imprison Yorshka in a tower above her church.