I'm guessing you're talking about the novel, Martial Emperor Jiu Xiao. After the male lead fused with the soul of the outer realm, he would indeed grow a head of silver hair. Just like Wu Po Jiu Xiao, it was a story of inspirational and heaven-defying cultivation. If you're interested in this type of novel, you can also look at novels such as Martial Proud of Heaven and Earth, Universe Fighter, and Peerless Martial God. They're all very popular! I hope you like my recommendation. Muah ~