User blog comment:SuBash/Questions/@comment-3061966-20130726212438/@comment-5004454-20130727164719

Let me pitch in too, ha :P I'm Zikimura, been here a while. So basically, since God Slayer is a cannon magic (meaning from the anime/manga) then yes, technically, you can fanonize whatever element you choose (almost).

The reason I'm mentioning all this is because, as you familiarize yourself in here, you will learn that there are other slayer types which are fanon. For those you need permission from the creator. However, that's a whole other can of worms you don't need to worry about yet. I'm writing this this so it helps clear out some misunderstandings.

In conclusion, cannon slayers don't have the "first come, first serve" rule. For fanon slayers, you have to ask the creator. Hope it helped and if it didn't, drop a message in my, the admins' or the veteran users' talk pages. Have fun mate :P