The Devil who speaks in Hands

Male Error404!Gaster Reader x Highschool DxD.
Y/N Xazoroth was the firts king of hell, but his thrown was taken forcefully by another devil named Sirzechs Lucifer. Y/N wasn't really strong at that time. He was just a child and Sirzechs claimes that he is the true ruler of hell. Sirzechs gave Y/N a chance to work for him and Y/N accepted. Y/N worked on a project called 'The Core'. A giant machine that would turn heat into useful resources, which were needed. But something went wrong, that caused Y/N to get erased from existence and land into the Anti-Void. After a few centuries, a mysterious individual appears and causes some problems. As it turns out, it was Y/N and he isn't in a very good mood. He came back to claim what's rightfully his. Will others remember him? Or will Y/N be not even a memory?
Disclaimer: I don't own anything. Just this story.