Lake Roccaluce (which translated from Italian to English means Lake of the Rock of Light), also called The Lake of the Fortress of Light is a lake found in Magix.
Lake Roccaluce is a beautiful lake which is located right in the middle of the Magic Dimension’s crater, in front of Alfea, Cloud Tower and Red Fountain, not far from Magix City. The mythical nymphs of Magix are said to live in its depths.
Water Nymphs' Village
The Undines live in the lake, near the Black Mud Swamp. They live in a village of air bubbles attached to water lilies. These bubbles are made of a special material that they make out of a plant called the Xylith.
16 years before season 1, when the Ancestral Witches about to attack Domino, Daphne acquired the Sirenix power to fight them and most likely, as a Harmonix fairy, activated the Source of Sirenix found in the Lake to obtain powers. However Sirenix had previously been cursed by the Ancestral Witches.
When the Ancestresses attacked Domino, Daphne tried using her Sirenix powers to fight the Witches but her powers turned against herself because of the Witches' curse and turned her into a bodiless spirit, and she became bound to the cave where the Source of Sirenix is found.
In the first season the Lake made some appearances as the home of Daphne's spirit, from where she attempted to communicate with Bloom.
After the Trix steal Bloom's Dragon Flame, she goes to Domino where Daphne tells her that she was once the nymph of Lake Roccaluce. Later, after a failed attempt to retrieve the Dragon Flame from the Trix by sneaking into Cloud Tower, Bloom and Sky wander across the forests and, on hearing Daphne's calling, Bloom goes to Lake Roccaluce where Bloom regains control of her powers after Daphne reveals to her that she still has the Dragon Flame in her and thought she had lost her powers because of a lack of confidence.
In Season 3, Valtor uses the Spell of the Elements to flood Cloud Tower with Lake Roccaluce's waters and he used the caves from under the then dried lake as a trap for Bloom. When Bloom used her Fairy Dust to free all the spells he had stolen, Valtor called the Spell of the Elements, and unvoluntarily the water of Lake Roccaluce as well, back to him, seemingly drowning him, though he survived and and trapped and kidnapped the Specialists near the Lake and brought them to the Omega Portal on Andros to use them to bargain with the WInx,
Lake Roccaluce appeared in Bloom's dream in the first movie, where Daphne mentioned that she needed to return to the Lake because her powers become weaker out of it.
Tritannus later entered Lake Roccaluce after stealing the powers of Nissa, the Selkie who guards the Ocean Gate of Magix, and he captured Daphne in hopes of knowing the secret of how to acquire Sirenix from her.
After the Trix attack Marion and Oritel, Daphne reveals to Tritannus that her Sirenix powers are protected by the Source of Sirenix found in Lake Roccaluce. Tritannus then goes to Daphne's cave in Lake Roccaluce and destroys the Source of Sirenix, causing the Lake to start drying up, and he then stole off Daphne's Sirenix powers from her and gives them to the Trix. The Winx, after defeating a pollution monster created by Tritannus, combine their powwers to those of the Selkies to restore the Source, which causes their Guardians of Sirenix to call upon Omnia, the Supreme Guardian of Sirenix, who gives Sirenix powers to the Winx, and the enter the Infinite Ocean from there.
When Tritannus fitted the Seal of the Pillar of Light in the Emperor's Throne, the throne's powers attacked him and drained him from his powers and he had to go to Earth to refuel himself. On crossing the Ocean Gate to Earth, Phylla, the Guardian of the Earth Gate, tried to stop him but was defeated by Icy. Phylla then went to the Selkie Village in Lake Roccaluce to ask the other Selkies living there to help her fighting Tritannus and the Trix.