User blog comment:IamJakuhoRaikoben/Chapter 387: Tartarus Arc: Part 4 - Father and Son, Review./@comment-5598380-20140607010852

Father and Son? I'm sure it's about Silver and Gray. Maybe Silver and his wife was killed because of Gray during the Deliora incident then Silver was revived by the Demon King. Maybe at that time, Silver is already a Mage with great powers. So, Silver became a Tartaros member, hunting demons like Deliora.