Silver tries to prevent him from utilizing the deadly spell numerous times, only to fail
The Devil Slayer keeps beating Gray to the ground, all the while he threatens him and tells him that he needs to suffer even more. Despite his grievous wounds, however, Gray rises up again, vowing to beat his opponent before taking the stance to use Iced Shell. Despite Silver telling him that ice will not work on him, Gray insists on using the spell to seal his opponent for eternity. Gray recalls the words of his friends, apologizing to them before seemingly using Iced Shell. However, his opponent manages to crush his spell, only for him to find out that in fact Gray tricked him again with an ice clone, saying that he will beat him without using that spell, because he does not want to make his friends cry; he uses a steel ball and throws it with his full force at the Devil Slayer using his Ice-Make: Vambrace, penetrating his chest with it and effectively defeating him. After his opponent congratulates him on his victory, Gray reveals that he knows that Silver is, in fact, not Deliora, but his father. 
Gajeel tells him to think about defeating his opponent first, so Gray proceeds rushing at Tempester, effortlessly freezing the Demon’s wind-based spell and then defeating him with Ice Devil’s Zeroth Long Sword
Gray refuses to kill Silver, albeit the latter insist that wishes to be killed by him. Confirming his declaration, Silver announces that he was, indeed, Gray’s father, but is no longer human, and let alone a Demon. Silver explains that he has been a corpse for seventeen years, taking part of an experiment held by Keyes, a Demon who can control the dead, shocking Gray. With a grin , Silver reveals to Gray that it was all for the sake of his revenge against the Demons who stole his family; apologizing to Gray for mistaking Atlas Flame for a Demon and freezing Sun Village. After realizing that Silver did what he did in order to protect him, Gray creates a sword of ice and proceeds to comply with his father’s wish-Silver apologizes to Gray for harming him. With his sword in the air, Gray recites his guild’s way of acting, but reminds himself that Silver is his father, dropping his sword and weeping furiously. Silver stands up, moving in to hug Gray, who asks if he could hold him for a little longer. 
Gray continues to embrace his father  until, that is, the defeat of Keyes comes to pass, which causes Silver to cease to be among of the living
When he vanishes completely, Gray tells Silver that he can finally rest; as he receives his father’s Ice Devil Slayer Magic in the form of a tattoo on his right arm, Gray states that as a Devil Slayer, he’ll crush E.N.D.  Afterwards, Gray returns to his previous location just to find an exhausted Gajeel being attacked by Tempester. He fires an ice arrow to intercept the Demon and, through unknown means, learns that Tempester is the one who poisoned Laxus and others, urging Gajeel to bring the Demon’s blood sample to Porlyusica. As Gajeel expresses his shock, Gray exclaims one more time that he will crush Tartaros.  Later, Gray is shocked when he hears Acnologia’s roar as the Dragon approaches the ruins of Cube. 
Afterwards, Gray is seen making his way through the ruins of Cube, when he stumbles on something familiar.  Gray then interrupts the battle of Dragon Slayers against the Underworld King, arriving just in time to freeze Mard Geer’s attack. Giving Natsu what he has found, Igneel’s scarf, Gray notes to Natsu that he should not lose it again if it is important to him. That is when Mard Geer finds his arm frozen, much to everyone’s surprise. He questions who Gray is, with the latter introducing himself as the Devil Slayer that will defeat the Underworld King.