Father Raul Piestro was the head priest of St. Vertinez before Temozarela was released. He is first seen coming to Ivan's home to speak to him about an essay he submitted about the ideology in the church. Piestro explains that he was part of the investigation into Ivan Isaac's after he submitted his paper on ancient religions, revealing that he was absolutely correct and that he was only reprimanded to stop further research. He then asks Ivan to come help them solve a puzzle which has all their experts puzzled: the Domas Porada.
During the research, Piestro reveals that his mentor, Father Ashley, led the investigation until he went crazy and killed all the other researchers before killing himself. This motivated Piestro to do the research himself. After the other researchers start to suspect his integrity, they asked for help from the Vatican. However, they are killed by agents of The Order of St. Vertinez.
After finding blood in one of the books, Ivan confronts Piestro. The head of St. Vertinez explains to him how he was visited by Temozarela in a dream and that he believes the archangel was sent to bring a new message from God. He then brings Gena Isaacs, Ivan's adopted sister and love and kills her.
When the Domas Porada is opened, Temozarela kills all the members of St. Vertinez, before turning to Piestro and killing him in a gruesome manner, asking "Did you not ask to be rid of sin or desire?"