The Seven Isles of Syren are a chain of seven islands located east of the castle in the strait between the Small, Wet Country Across the Sea and Wudz. The Isles' only residents are the Syren and Syrah Syara.
The seven islands are Syren, Well Island, Cave Island, The Twins, Star Island, and Moon Island.
The Isles are the main location in Syren and provide the setting for most of the book's storyline.
Septimus, Jenna and Beetle crash landed on Syren Island during a storm because of a lightning strike to Spit Fyre's tail.
Septimus then discovered that there was another person- Syrah Syara- on the isle. However, Syrah is controlled by a Syren whenever she goes into a tower. He tried to help Syrah seal the way into ice tunnels, because Tertius Fume wanted to use them in his plans.
Meanwhile, Lucy Gringe and Wolfboy were brought to CattRock, where Theodophilus Fortitude Fry stole Miarr Catt's Sphere of Light and placed it on to beach of Syren isle.
After some time passes, Nicko, who is skippering the Cerys, hears Syren's call and sails the ship onto the rocks. Fry and the Crowe twins free the army of warrior Jinn after a bloddy fight, and Tertius Fume commands them to attack to the Castle via the Ice Tunnels in order to conquer it. However, Septimus's Jinnee, Jim Knee managed to freeze them all just in time.
Jim Knee also, for Septimus's request, captures the Syren in a bottle and everyone flees the Isles. Miarr Catt is left to tend to his sphere of light.