One thousand years ago, something happened in Canterlot. Two Princesses entered a room, and only one walked out again. The people were told something to keep them quiet, to keep them from talking, but it wasn't the truth... only Celestia remembers what actually happened.

Dawnstar is a much darker take on the story of the two sisters - opening with a more believable set of events that may have occurred the day Luna was banished, then following Celestia as she lives a thousand years without her sister. Unlike my other stories, it's almost completely lore compatible - it fits so well it's practically a conspiracy theory.
The only thing that doesn't click in perfectly with show lore is the conversation between Luna and Celestia at the end, but the one that took place in the show's second episode no longer made sense, so I call artistic liscence ;)

Hope you enjoy it!