Equestria is a land of magic and harmony, a peaceful realm ruled by immortal and benevolent monarchs. At what cost is this possible?

Following the discovery of a strange and powerful device, Twilight Sparkle is whisked away to the edges of a land she thought she knew so well. Here, surrounded by ponies whose very existences have been kept secret, she must contend with vicious enemies, hostile allies, and the truth.

Chapters 1-16 edited by KiltedKey

One by one, Twilight and her friends must come to terms with the consequences of being the Elements of Harmony.

These stories take place in the intervening time between Season One and Season Two,
with the exception of Ditzy Doo: Muffins, which takes place early in Season One.

The series continues in the sequel, Secrets and Lies.

Pony Psychology has a TV Tropes Page.

The Ponyspawn have invaded Equestria, and it is up to the newest addition to the Grey Wardens, Twilight Sparkle, to find the means to drive them back! With her friends and allies at her side, can Twilight defeat the evil tide before all of Equestria is devoured?

The Sequel, Pony Age: Catalyst, is available.

Twilight Sparkle is summoned to settle a legal matter involving The Great and Powerful Trixie... What in Equestria did she do now?