The Tears of Gaia. An artifact of unmeasurable magical power from the Ancient Days, when the Others ruled the land. If found, they would be the discovery of the century!
At least, those are Twilight Sparkle's thoughts. But something is stirring in lands to the south. Soon she will find that she and her friends are not the only ones who are after the legendary Tears. And so what starts as a simple research trip is soon to escalate into the greatest journey of the young ponies' lives, filled with new friends and foes, incredible danger and great adventure!

Accolades:
EqD featured- 21/09/2012
Now with its own TVTropes page right here!

NOTE: While I do appreciate all comments I get on this story, I would personally prefer if they could say a little more than the typical "Awesome chapter, I love it!" or whatever. What do you love about it? What struck you in this chapter? What would you like to see explored or expanded? Are there things you don't think are working and if so, how could they improve?? I have a pretty determined vision for this story, but it wouldn't hurt to know for the future!

SF (canon species only; no humans) Ponies were magically and genetically engineered to be the perfect servitor race. They are powerful, adaptable, intelligent and completely under the control of their creators. A laboratory accident frees one such pony from her mental chains, but how can one mare save herself and the rest of her kind if she doesn't even know she's a slave?
This is not the Equestria you know and these are not your little ponies... not yet, anyway.

Tags: Adventure, Diamond Dogs, Gryphons, NO HUMANS (did I mention that already?)
Other tags: historical, mind control, Clarke's 3rd Law, excessive use of high energy physics, before they were famous.
Detailed review by PaulAsaran.
Cover art by endrome , used with permission.
Russian translation (partial -- 'unofficially' completed in the comments)
A Soot-Covered World, book 1.