I want to write a fantasy novel and I have an idea.?

Wow, cool idea.. would definitely read it :) The back story and history is a good idea as it helps draw the reader in to the world and keep them interested. Just a little niggle of mine, man slayer doesn't sound mysterious and powerful, so I would say to use a Japaneses name that sounds cool. Google translate to phonetic japanese is a good way to get cool sounding names eg." Kuei-jin, Ansatsu