Luna has had enough of Celestia's games, and has found the perfect means of revenge. Using a long-forbidden spell, she transforms her sister into little more than a small filly, all so she could pull the greatest prank ever. Unfortunately, she soon learns that before you fool around with dangerous magic, you really need to read the fine print...

A sequel can be found here.

Some of the ponies in Ponyville had each received an invitation from an unknown sender to Stonehallow Manor. Thinking that nothing bad would happen, they all reluctantly accepted the invitation and headed to the mansion located past the Whitetail Wood. No one had been to the mansion until now where they soon face a terrible case in their hands. Will these ponies be able to solve why this is happening?

Luna discovers something hidden from Celestia for twenty years, now, with emotions running high, she enlists the help of the Mane 6... but what seemed to be a single mystery, soon reveals a darker and much more complicated plot that will soon decide the fate of Equestria.

Check out the Empty Room TV Tropes Page (Warning: Spoilers!)

Revised chapters edits and proofing (with many thanks) by: lammy, Trevor, Nick Nack, Fifth Alicorn