"There were 2 things my father had that you lack Raum, a full soul and free will"-Sebastian Michaleis
The Redeemed One also known as The Demon That Defied the Devil is the deceased father of Sebastian Michaleis. He was a renegade demon that served Heaven and fell in love with a beautiful Angel women, Sebastian's deceased mother, Lisa.
In the Hellsing universe, Father Anderson kept record of the Redeemed One and used his fighting style to slay vampires. The story of his origin was that the Devil had a demon steal a soul that was used to make an angel and merge it with a raven, creating a powerful demon. However, the demon grew sympathetic of humans(according to Anderson he said he was still an angel he just had a "demon body" and because of this he says Sebastian as well is an "Angel with a demon's body"), and even fell in love with an Angel women named Matilda. Satan was furious and had him exiled to Earth, The Archangel Gabriale saw the sadness in the renegades heart. The demon even bowed to the angle asking to serve Heaven, he did so and was married to the women he loved. Years later she had a child, a demon with angle blood, Sebastian, and when they were on Earth and Sebastian was only 9, Satan had one of the Demon Earls, Count Raum, kill The Redeemed one and Lisa and abduct Sebastian. However Sebastian held on to his mother's Rosary and defied the devil. So he was taken deeper into Damnation to Tzneetch and Nurgle, Nugle infected him with the Black Plauge, and Tzneetch placed nightmares in his head that made him kill in his sleep. Soon by the age of 14 Sebastian used the portals of Hell to escape to numerous time periods (for example Ancient Egypt), he hid until he was 22, were he stopped in Victorian England where he made a deal with a boy who may not shared his faith in God, but shared his pain in loss of family, Ciel Phantomhive.