Bookish idea

I've been thinking about an old character I made up as a kid, and think I can redo him to fit the into league world. But i'm not really sure how to write about him. I have a neat idea about a Piltover/Zaun thing that could both show my character and be an interesting event in league history. I've also been thinking about writing. Is there anything legal related that I should know before I write anything? Also, is there any writing tips that anyone would like to share?