Terrence came to the New World with Jacques Cartier's vessel, The Emerillon, in 1535 CE. He was a mortal infernalist responsible to consecrating unholy ground atop the island mountain, in service to his lord Methatiax, who kept him preternaturally young.
Terrence Bouville received the Embrace of Connaught in 1653. However, the newly created vampire never emerged from his grave. Methatiax discovered an ability to claim those who have been buried in the mountain, and he scoured the soul of his acolyte creating an empty receptacle in which to place his own essence. From that point on, DeBouville's body became Metathiax door to the mortal world, and the demon has walked the streets of Montréal for centuries, guiding Sabbat and mortal alike with his dark influence.
After many centuries, the demon thought he had a better deal and agreed to place the tortured soul of Santiago DeSoto in the empty shell that was once the body of Terrence DeBouville. This allowed it to hunt for Sangris the Serpent, for Metathiax has promised Sangri's soul to his demon sibling Bothothel in exchange for help in breaking his ancient prison. Unbeknownst to Bothothel, Metathiax altered DeSoto's mind and new body, making him believe himself to be Sangris. In this manner, the demon hopes to trick Bothothel into claiming the wrong soul.
Metathiax has therefore put the Inquisitor in the care of the Sabbat scholar Marie-Ange Gagnon. Gagnon is being corrupted by the confused soul she believes to be Sangris'. Now, the demon waits for its pawns to play their parts until its prize surrenders himself.