So Blizzard’s having this contest and I wrote something for it. Given that this is a piece of fiction written within an established universe it is, in essence, a work of fan fiction. Now there’s a lot of fan fiction, from the drabbles that put Harry Potter in bed with Draco Malfoy to the novels published in the universes of Warhammer or Star Wars. There are some things, in my experience, that separate good works of this type from the bad ones.
It all comes down to doing the research.
If you want to avoid derailing a character’s development, ensure your work fits into the tapestry of the universe and match the tone of previous works while providing your unique voice, you have to know the facts about your piece back to front. If the universe began as movies, watch them; as novels, read them; as games, play them. Know the characters, settings, themes and moods. A lot of established fictional universes have on-line resources, from basic fan-sites to extensive wikis – make use of these resources.
There’s established lore out there, and if you ignore it, by either not researching it or choosing to omit it, bad things can happen. It might not make the work entirely unsuccessful, but you might have to weather criticism such as “This character would never act that way,” “The timeline of these events is all screwed up,” or “[insert author name here] doesn’t know how to write women properly.”
Walking into a place filled with lore looking to tell a new story can be a lot like walking into a minefield. If you don’t watch your step, your journey will end very abruptly and messily.
Just be careful.