The Sirenix Book is a book introduced in Season 5.
It has a burgundy cover with silver designs in the corners and a gold crescent moon in the middle.
The book holds the Sirenix Quest, its riddles, Sirenix Guardians and from the Sirenix Guardians - Harmonix. This book has been in existence for centuries as Faragonda calls Sirenix "the ancient power of the oceans." Its powers had been sought after before, evident by Stella's Sirenix Guardian telling Stella that she is one of the best fairies she has ever met. Before the Winx, Daphne had completed the Sirenix Quest and planned to use this power against the Ancestral Witches who destroyed her home. But before she could use it, the Ancestral Witches placed a curse on Sirenix and transformed Daphne into a disembodied spirit.
This book is found in the Alfea's Magic Archive. It cannot be opened unless all the fairies seeking the power of Sirenix are in agreement to open the Book together. The Winx were only able to achieve unity after completing the Challenge of Graynor and earning the Boon of the Ancestral Spirit of Nature. This boon, known as Nature's Key, was what allowed the Winx to open the Sirenix Book.
At first, they could not open it, until the Winx won the challenge in Graynor, and gained the Nature's Boon to unlock the book and open it. The Sirenix Book gave the Winx the Sirenix Boxes and their Harmonix powers. It also gave the Winx Club a warning about the curse that was bestowed upon the power; if the Winx did not complete the Sirenix quest in one lunar cycle, they would lose their powers.
During the time, it gave Winx riddles that leaded them to the Gem of Self-Confidence through Andros to Solaria, Gem of Empathy through Melody to Zenith and Gem of Courage through Linphea to Domino. When final gem was acquired, the book disappeared as it was no longer needed.
- In the Italian version, the Book has a male voice, while in English version it has a female voice.
- The Italian voice actor is Marco Bassetti, and English voice actress is Kari Wahlgren.
- The Sirenix Book's appearance is similar to the book that was used to summon an Anthropomorphic Monster, a creature that looks like Professor Avalon in Season 2.