This story is a sequel to In Her Majesty's Royal Service
After guardsponies Storm Stunner, Crack Shot, and Check Mate proved instrumental in stopping an interdimensional incident that threatened to annoy the city of Canterlot, the Royal Guard made a realization: perhaps they might just be able to serve functions beyond pulling aerial chariots and trying not to blink in public.
Now months later, they're finally starting to get somewhere with each of the odd regimens they've designed; it's a shame that three of their number will have to miss the progress to follow. In recognition of their prior bravery, quick thinking, (and to a smaller degree their dumb luck), Princess Luna has given Storm, Check, and Crack Shot a special assignment: to visit the lands on the borders of pony control, to sample the local flavors, and to maybe even take a picture or two. One might dare to call it a vacation.
However, expectations mean little so far from home, and despite Luna's wishes to keep the guardsponies out of harm's way, the world can easily change in a thousand years. The three guardsponies may be forced to deal with the inconvenience of their vacation turning into an adventure.
First Story: In Her Majesty's Royal Service