Season 4

The girls learn about their new enemy, known as the Wizards of the Black Circle, who stole the magic from Earth, and that there is one last fairy that they are looking for. Now, the Winx Club must use the Tree of Life in Pixie Village to travel to Earth and find that fairy — but they must first battle a monster that has caused all the Pixies to mysteriously vanish.

While Love & Pet slowly becomes popular in Gardenia, the Wizards of the Black Circle arrive on Earth and begin their search for the last Earth fairy. Meanwhile, the Specialists have recently arrived on Earth, where Sky discovers Bloom with Andy, an old friend of hers.

The Wizards invade Love & Pet and bewitch several of the animals. The Winx girls must round them up and find a way to reverse the spell. Meanwhile, Mitzi shows her affection for Brandon after he saves her from one of the bewitched animals. This begins to infuriate Stella.

Both the Winx girls and the Wizards of the Black Circle discover the identity of the last Fairy on Earth —Roxy, a waitress at the Frutti Music Bar. A huge battle ensues between both sides over the new girl and only her belief in magic can help the Winx Club turn the tide. The Winx girls earn their Believix after Roxy believes in fairies.

Thanks to Roxy, the Winx girls have earned their Believix, but their powers have still not fully evolved. Meanwhile, Roxy is being chased all over Gardenia by the Wizards, while a mysterious female voice encourages Roxy to accept her magical powers.

As Bloom tries to reassure Sky that she and Andy are just friends, Roxy, while holding the White Circle, is possessed by anger and rage and goes to take on the Wizards of the Black Circle.

Musa's singing attracts the attention of a record manager named Jason, who offers her a record deal. Riven's jealousy toward Jason causes him and Musa to drift farther apart. Meanwhile, the other Winx girls and Roxy suffer many failed attempts to get the people of Gardenia to believe in fairies. Only when the girls help extinguish a fire created by the Wizards do the people slowly regain their belief in magic.

Roxy discovers that the Wizards have abducted her father, and she is captured herself when she gets home to inform her father of her magical abilities. Artù, Kiko and the Love & Pet animals mount a rescue mission to save both of them, but Artù is injured by Gantlos in the process, which allows Roxy to awaken her dormant fairy form.

Roxy is put to the ultimate test when the Wizards of the Black Circle threatens to destroy all of Gardenia and its citizens if she does not surrender.

The Winx girls and Roxy must deal with their new popularity within Gardenia while also dealing with a pair of animal smugglers.

The Winx girls' new popularity infuriates the Wizards of the Black Circle, so in a plot to make people hate fairies, they offer to transform Mitzi and her two friends into fairies. Meanwhile, Jason invites Musa to his wedding, and the Winx girls teach Roxy the basics of being a fairy.

Tecna reveals that she has created a virtual world in her computer to hide the White Circle, but while the girls go to perform at the Frutti Music Bar, the Wizards enter the virtual world to find it.

The Winx girls travel to the island from a vision of Roxy's, the mystical world of Tir Nan Og sealed within the White Circle. Upon arriving, a mysterious figure keeps calling out to Roxy and a dark force soon abducts the Winx, taking them to the prison of all Earth's fairies. After freeing the Earth fairies, they reveal that they want revenge against the humans who imprisoned them, and declare war against all of humanity in turn.

Diana, the Earth Fairy of Nature, begins the war against humanity by transforming Gardenia into a huge jungle. The Winx girls must deal with this new menace, plus the kidnapping of their boyfriends, except for Nabu, who held strong against Diana. In the process, they learn from Miss Faragonda that there's another level of transformation for a fairy, an evolution of Believix, called Sophix.

The Winx gain their Sophix powers as they enter the Amazon Rainforest, where Diana has made her new lair, but after they split up, Flora, Musa and Layla are captured while saving the Specialists. Meanwhile, Bloom, Stella, and Tecna locate the source of Diana's power: the Sacred Bud.

The Winx Club and the Specialists manage to escape Diana's fortress as they realize that the Sacred Bud is connected to her; the more of the forest that is destroyed, the more Diana is weakened. The girls must save the forest as well as Diana, and also somehow manage to convince her to release Gardenia from its plant prison.

The Winx form an unlikely alliance with the Fairy Hunters to help one of them after Duman comes down with an illness. They travel to the Sibillini Mountains in Italy, where they ask the Fairy of Justice, Sibylla, for help.

Aurora, Fairy of the North, comes to Earth, freezing it over and threatening to send the planet into another Ice Age. The Winx, using another evolution form called Lovix, which is winter-themed, confront Aurora.

Bloom and the rest of the Winx face off against the fairy of war, Nebula, while also trying to protect Roxy from her. Bloom fights Nebula with the agreement that Nebula drop her campaign for revenge if Bloom wins.

The Winx girls return to Tir Nan Og with the Wizards of the Black Circle, but they end up in the fight of their lives when the magical kingdom is in danger. Nabu makes the ultimate sacrifice to save the kingdom and dies in the process, causing Layla to seek revenge for his death. In the end, she leaves the Winx Club and joins Nebula's army.

Nebula captures Morgana and conquers the magical kingdom of Tir Nan Og. Then, she leads her army into the Omega Dimension where the remaining Wizards are hiding. After freeing Morgana, Roxy discovers that she is Morgana's daughter. Later, the Winx girls must face Nebula's vengeful army, led by their new lieutenant — Layla. Morgana and the Winx girls are able to convince the Fairies of Vengeance not to seek revenge, but now must also convince Layla and Nebula of the same.

The Wizards of the Black Circle flee as Layla and Nebula chase them toward a dead end. Determined to avenge Nabu, Layla teams up with Nebula to destroy the Fairy Hunters, but both are easily overpowered. The Winx catch up with Layla and Nebula and all eight fairies use convergence to freeze the evil wizards solid. Afterwards, Layla uses the remnants of Nabu's spirit, combined with the powers of the Fairies of Tir Nan Og, to restore the kingdom. Morgana proclaims Nebula the new Queen of Tir Nan Og, and then returns to Earth, where she is reunited with her husband, Klaus, and her daughter Roxy, while Layla returns to the Winx. With Roxy making the decision to study in Alfea and Earth's belief in magic.