"One of the Seven Archangels. His name means "God's command," and he is said to be an angel of death. His role is to watch over human souls and prevent them from sinning. He also governs the phases of the moon, but as a result of telling that secret to humans, he fell from grace. He is said to have silently left the heavens with dignity. He also has an evil eye that can hurt anyone it falls upon."
Sariel is the name of an archangel from Judaic tradition. His name means "Command of God". In the Book of Enoch, he is one of the four holy archangels and is of "eternity and trembling", in the Qabbalah he is one of seven angels of the earth, and Origen identifies him as one of seven angels who are primordial powers. He is a prince of pressence and an angel of healing, like Metatron and Raphael respectively, and is one of few benevolent angels of death.
Sariel is fought as a boss in two of Devil Survivor's routes. He, along with his palette swap Anael, appear in Yuzu Tanikawa's ending, to oppose the protagonist's attempt to escape the lockdown, and in Naoya's ending, to attempt to dissuade the protagonist from staying with Naoya and becoming the King of Bel.
They will also appear in Overclocked on Naoya's 8th day, assisting Metatron in the final battle (if the protagonist spared the demon tamers).