As an employee in the Fabled Stables, young Auggie must protect all fantastical creatures, even the irritatingly talkative furry tails that have attached themselves to the human residents of Rainbow's End.

Auggie loves his job at the Fabled Stables, but he fears the day when it will come to an end. Fen keeps dropping hints that caretakers don't stay forever, and it's giving Auggie the grumps. Thankfully, there always seems to be a new stall to fill. This time, the stables set Auggie on a quest to rescue a beast called the Shibboleth but, the portal leads Auggie and Fen to the lair of the evil Rooks! In the dark, damp dungeon, they meet one mysterious...