I'd like to start out by mentioning that when I first heard about your fanfic through the @Ironstylus post, I was a little hesitant to click. Mostly because several of my brief and painful delves into fanficdom have been excercises in mental cleansing, over exposure to hormones, and terrible writing.
Secondly, you've done none of those things. Your story was interesting, and your characterization is very strong. Plagueis as an OC character in particular is well done. He puts out the " I could kick your ass in a heartbeat " vibe rather well. In fact, you seem to capture all of the League's champions in a good light, keeping close to the script, and not flying off in some horrible "My Immortal" level escapades. There are small moments where there are slips in character, but eh, it's a fanfic, Artistic license is a perfect validation in these cases.
Also, about purple prose... me gusta.
Keep up the good work, thou hast earned an upvote.
PS. I hope IronStylus reads your thread. You're quite talented.