Astraeos was a Librarian of an unknown Space Marine Chapter that in late M32 or early M33 was targeted for elimination by the Grey Knights under the orders of Lord Inquisitor Castus Izdubar, following the loss of the Athenaeum of Kallimakus at Apollonia. He, and three other members of his Chapter survived -- its former Chapter Master, Thidias, its Chapter Standard Bearer, Kadin, and another Astartes, Cadar. They secured transport on a rogue Adeptus Mechanicus ship, the Titan's Child, under the captaincy of a rogue tech-priest, Carmenta, and fled for the Eye of Terror. Entering the Eye the ailing vessel was captured by the Harrowing, a band of Chaos Space Marine renegades. Cadar was killed in the assault and turned into a daemonhost by one of the Harrowing's sorcerers, Maroth, who removed o