Jessica Burkhart 
Hidden Treasure [EPUB ebook] 

Bella must go on a special quest for a magical crystal in order to save her beloved Glimmer in the fourth book in the Unicorn Magic series!After a sparkly visit with her cousin, Violet, Bella is having a fun time at a party her parents are throwing in honor of Violets visit. But there is one unexpected guest Bellas aunt, Queen Fire, who rules over the Dark Forest. It turns out there is a magical crystal hidden deep inside Crystal Castle, and Queen Fire wants Bella to find it and bring it to her. It holds special memories that her aunt wants to have back, and if Bella cant complete her request, Queen Fire will take Glimmer away! Can Bella figure out how to find the crystal and save Glimmer?