Seth Disarmonia is a creation of Discord, who's become friends with the Wielder of the Elements, but that's the main story, Spawn of Disharmony. This is side stories of that fic. Have fun.
Before he was defeated Discord created Seth. Now Seth is in Ponyville where he starts to become friends with the ones who defeated his creator, and even start developing feelings for one of them. A certain light blue pegasus.