"It all comes back to Princess Luna, since Celestia is interested in learning about ethereal magic, such as friendship. Luna has begun devoting herself to learning the magical properties of physical creatures... So, Banshees, Griffons, Hydras, and most importantly, at least as far as I'm concerned, Dragons."
***
Stoneheart is Luna's first student, well, student may not be the best word for him. She didn't teach him from youth, but she still trusts him. At least as much as Celestia trusts her student. In reality, Stoneheart is a scholar, teaching, exploring and researching by order of Princess Luna. Hoping to change all of Equestria's perspective on the most mystical of all creatures, Dragons.
And now he's received a special assignment, go to Ponyville, a location in which there have been more dragon sightings reported in the past year then most places see in twenty, and do research on its residents. But there is more to this assignment than meets the eye, a major event for Dragonkind is on the horizon and Stoneheart is somehow implicated...
And Twilight Sparkle has graciously accepted to host him.