Once upon a time, Spike went for a walk.
While on his walk, he was judged by an ancient alicorn, lodged with griffons, parlayed with air pirates, charmed a maiden of a mystical race, and dealt with the scourges of hate, fear, and racism while deliberately drawing the armies of myriad nations to the brink of global war.
Once upon a time, Spike went for a walk, and did all of this so that he could keep a promise to the one that meant the most to him... Twilight Sparkle.
In the first of three books, Pillars of the Sun (Chapters 1-15), Spike is devastated by Twilight's fate and grows more and more despondent as he attempts to understand what has happened to his dearest friend. A gentle nudge from a pony he trusts sends him looking for answers. When that nudge becomes a push he unravels ancient secrets... and risks losing himself before his attempt to rescue Twilight can even begin.