Silver was an Ice Devil Slayer. Silver Fullbuster is the father of the Fairy Tail Mage, Gray Fullbuster. Silver died in X774 along with his wife, Mika. Not much is known about Silver's past other than the fact that he supposedly died during Deliora's attack on his village. At one point in time, however, Silver was seen laughing with his son, telling him to become strong.After his death, Silver's corpse was stolen by Keyes for the purpose of experimentation, among the bodies of many others. Keyes' experiment ended up being a success, and for seventeen years, Silver "lived" as a normal human being would. However, Silver then used his new "life" to exact revenge on the Demons that stole his family from him; masquerading as a loyal member of Tartaros, (having been inducted into the guild, courtesy of Mard Geer). Silver learned Devil Slayer Magic and covertly killed any and all Demons he came across, all in preparation for his ultimate plan: the destruction of Tartaros. After seeing that his son was alive and well and witnessing Gray's performance at the Grand Magic Games, Silver decided to abandon this plan because he realized that he didn't have the right to fight for Gray and his deceased mother as his own hands were too dirty, presumably from his official missions for Tartaros. (Source: Fairy Tail Wiki)