A strange creature has appeared in The Frozen North. Princess Twilight has been dispatched to deal with it, but Princess Luna has also sent along some help. Unfortunately, Twilight doesn't consider Princess Luna's choice to be the best possible one.
But Twilight is going to need all the help she can get when she comes face to face with a creature of legends and myths. Something so powerful that even Starswirl feared it, and something so dangerous that even the Princesses are wary to challenge it.
Can a newly minted Princess and a shamed show pony manage to defeat this creature? If not, then all of Equestria will be in danger.

Written for EQD Writer's Training Grouds #006

Update: Sequel stories
A Shattered Stone
Trixie's Task