Brother Renault was a Hammerite who lived 50 years before Garrett first entered the walled-off section of the Old Quarter.
He was a good friend of Brother Murus, who asked Garrett to bury Renault's body in the cloister graveyard. If dropped into his grave before Martello, his thankful voice is heard telling Garrett of the secret room in the winter tunnels.[1]
Renault's Observatory
Brother Renault did the Builder's work studying the movement of heavenly bodies in the observatory in St. Jenel's tower[2]. He discovered the curious ability of the Lunar Pool to bless hammers when moonlight was focused upon it through the telescope, making them into holy symbols[3]. He probably died before the Cataclysm began. A grave was made, but his body somehow wound up in the Cathedral cellar.