Osiris is one the chief Egyptian gods and the first king of the Nile. He is the son of Geb and Nut. His siblings are Set, Isis, and Nephthys. He married his sister Isis and became the father of Horus.
Although there are many different variations on how he died, Set is usually said to be the murderer. After his death, Osiris became Lord of the Underworld and Judge of the Dead.
Osiris was also known as a symbol of resurrection. Isis performed a magic ritual whereby she restored him to life. He is typically depicted as a bearded man wrapped in mummy bandages and holding a crook and a flail to symbolize his kingship.
Retrieving his coffin is part of the Challenge Quest Isis' Search for the Coffin , where Seth captured it and tossed it into Naraku. His body is torn apart by Seth before the Challenge Quest Osiris Resurrection in order to keep him from reviving. His body parts are collected and he is restored at the end of the quest, thanking his wife Isis and decides to aid Flynn by joining him for helping him resurrect. He does admit that he is missing one part of his body (his genitalia) and asks that he does not tell Isis.
"God of the dead in Egyptian lore. His consort is Isis, and his son is Horus. He was the god of vegetation, and once ruled Egypt after the sun god Ra, but was murdered by his brother Set. Thanks to Isis's work, he was resurrected from the dead and became king of the underworld. He was not feared, but rather worshiped as a god who brings eternal happiness in the afterlife."
"God of the dead in Egyptian lore. His sister-wife is Isis. He was the god of vegetation, but was murdered by his brother Set. His body was chopped into several pieces and scattered throughout Egypt, but Isis gathered most of the pieces and returned him almost to normal. He left the land of the living to his son Horus and became the king of the afterlife."
—Devil Survivor 2 Compendium
Osiris appears as one of the demons of the Deity Race. He can be summoned once the Protagonist reaches Lv. 53 or above.