Changeling hives are vanishing with no trace left behind, who, or what is hunting the changeling race? And what fate awaits Queen Twilight Sparkle and the rest of her hive?
The barrier preventing monsters from returning to the surface was broken. Yet a fail-safe was placed to ensure that the humans would never see them again. New creatures appear in a cave in the Everfree, and nopony is prepared for their new visitors.