The Sunken Kingdom - The Obsidian Spindle Saga, #8

The Fairy Realm has been fractured for too long. Now, The Sunken Kingdom must rise. Lucy has awoken the great dragon Farzinium, and taken her rightful place as its rider. They are a formidable force, and for the first time in generations the Fairy Realm has a chance at salvation. .but it will not be easy. Nimue controls the devastating might of the Unseelie courts and seeks to reunite the four pieces of the legendary Xirgolov on her path to unlimited power.
If she does, then there will be no stopping her. However, if Lucy, Gwen, Red, and Rose can find the Xirgolov pieces first, then they have a chance to raise the Sunken Kingdom and restore the Fairy Realm to its former glory. Surrounded by a powerful group of surprising allies, they prepare for a final battle with the fate of the Fairy Realm, Earth, and the whole universe hanging in the balance. Will they rise to meet the moment? Join the heroines of The Obsidian Spindle Saga in the final book of the second arc that will upend everything you know about the universe.