Someone trapped in the caves of the cold winter, a lonely human trapped but found after thousands of years. See the human's past and the now present. See how his heart was first cold, then warm, but turned into a harsh cold again.
Something starts to freeze over in the everlasting winter of the north, endangering the Crystal Empire, so the mane six goes and tries to stop it but finds something broken. Can they fix a heart the froze over because of a trust that shattered like fragile thin ice.