Dewey Decimal was the head librarian of the Royal Canterlot Library. When Twilight Sparkle returns to her hometown to perfect an ancient long-distance teleport spell, Dewey sees an opportunity to escape his humdrum life. Dragging his childhood friend, 'Blank Flank' Steven, along with him for the ride, the pair find themselves in lands far from the safety of Equestria. Facing strange monsters, spirits and races while making few friends, they'll test how much a cutie mark really defines a pony.

When Twilight had finished her explanation of the MMMMystery, nopony in the carriage had any doubts about her conclusions, but that doesn't mean their weren't still questions that needed answering. Fortunately, a nearby professional was at hoof to assist. With deductions as strangely concise as her own, Twilight faces the consequences of this unraveling conspiracy, but still, is everything as it seems?

It has been ten years since the founding of Equestria. The pony tribes have overcome their differences and have built a new society of unity and order, but little did they know their new found peace would lead to such ruin. For no action can exist without an opposite. No great harmony can be created without Discord being born. Now Princess Platinum, Clover the Clever, former-chancellor Puddinghead and Commander Wonderbolt must find a way to help their gods overthrow their new tyrant, while trying keep the country and themselves from tearing apart.