Princess Cadance has lost the element of predictability in her life. After finding a mysterious rose in the mountains things aren't what they seem. Like King Sombra being dead? Forget about it! Sombra speaks of a threat against the empire that even he isn't sure on. Explosions follow them almost everywhere and Cadance just can't seem to shake the creepy feeling of her companion off. With only her own sanity, an antisocial unicorn, and a collection of horrifying 'fairy tales' to guide her, Cadance isn't sure she'll make out alive.
Edited by: ElderXelpud
Spoilers in the comments.
Takes place in the Iceverse and between seasons 4 and 5 of MLP:FiM canon.