A supremely powerful wizard who aspired to become the greatest sorcerer of the magical universe. He turns people into monsters that willingly serve him and places a magical mark that looks like a "V" on other people so that they too will serve him. By doing so he hopes to be able to conquer each planet or realm. He was created from a dark spark of the Dragon Flame by the Ancestral Witches and in their youth, he and Ms. Griffin were formerly magical companions. During that time he meets Bloom's parents, Queen Marion and King Oritel of Domino, who are both stronger than he is. He was with the Ancestral Witches when they destroyed Domino and he supposedly killed Marion and Oritel the day Domino is destroyed (which is later revealed to be a lie), but not before they were able to imprison him in the Omega Dimension. Seventeen years later, the Trix are sent there as well, where they freed him from his prison. They escape and he conquers the seas of Andros and restores his lost powers with the energy of the second sun of Solaria. He then starts stealing all the magical secrets and spells of all the realms of the Magic Dimension and planning revenge against all those who helped defeating him, hunting down Faragonda, Griffin and Saladin and making their lives miserable since they, together with Marion and Oritel, were part of the Company of Light that fought and defeated the Ancestral Witches and Valtor himself. He also hunts down Bloom, the daughter of Marion and Oritel, as a way of taking his revenge for being imprisoned in the Omega Dimension by them. In the second-to-last episode of season 3, Valtor transforms into a demon and unleashes a spell that almost destroys the three schools and Magix but the Winx manage to release the spells that Valtor had stolen. In the final episode, Valtor is destroyed by Bloom when she extinguishes his own Dragon Flame. He functions as the primary villain of season 3.

Also called the Shadow Phoenix is the primary antagonist of the second season. He is an ancient being from the beginning of when all things were created. In the 4Kids dub, he was created when a man sought to control the shadow fire and merged with it. The Shadow Phoenix is the diametrical opposite of the Dragon, and like the Dragon, he is very powerful. The dragon is the source of energy and light while the Shadow Phoenix absorbs energy and magic, making his essence the opposite of the Dragon's Flame. He is the cause of the destruction of Domino, since the Ancestral Witches were his servers who acted upon his orders. After the Ancestral Witches were defeated, the Lord of the Templars of Roccaluce defeated Lord Darkar and sent him into a deep slumber from which he woke up at the beginning of the second season, possibly by the reappearance of the Dragon Flame in the magical universe. He kidnapped the pixies, rescued the Trix from their prison and used the Codex and Bloom's Dragon Flame to open a portal to the Realm of the Relix. The Shadow Phoenix nearly succeeded in his plot to claim the Ultimate Power and rule the magical universe, but in the end, Darkar was defeated by all six Winx Club members and was destroyed for good.

The Trix are the main villainesses of the series. They managed to "steal" Bloom's power, The Dragon Flame until Bloom, with Daphne's help, realised that she had never lost her powers, but was unable to use them because of her doubts, and therefore regained her powers and defeated the Trix. They were arrested and sent to the Fortress of Roccaluce in the end of the first season, but they escaped with the help of Lord Darkar in the beginning of the second season. He gave them their Gloomix which multiplies their strength and magical abilities tenfold. In the third season, they worked with Valtor. He gave them a power-up called Disenchantix, which is the opposite of Enchantix. They made a comeback in the second film as minions of the Ancestral Witches. The Trix returned in the fifth season and gained Dark Sirenix that Tritannus stole from Daphne and gave them. They are the main villains again in the sixth season, at the end of which, they are locked inside the Legendarium book for good. In the Seventh Season of the Winx Club the three witches return back into the real world after Brafilius finds and unlocks the ultimate power and accidentally releases the Trix from imprisonment in the Legendarium world. In the episode 22 of Season 7, the Trix kidnapped Brafilius and they take revenge on the Winx for trapping them then they were defeat by the Winx in the finale episode

Icy: The leader and the oldest of the trio. She is the witch whose powers are derived from ice, snow, frost and sleet, which starkly contrasts with Bloom's powers deriving from fire. She enjoys torturing fairies and despises Bloom and the Winx. Therefore, she is most competitive with the girls for the whole series. In comparison to her sisters, she is more aggressive than Darcy, but calmer than Stormy. She has bluish white hair, and has a dark teal hair tube piece in her hair that ties it into a high pony tail with three ice blue diamonds on it and a blue outfit with an 'I' in the middle and dark blue boots. In season 2, Darkar gives Icy a light blue necklace (Gloomix) that makes a perfect shape around her neck then makes a wider circle shape and ends with a diamond. Icy is also given the form Disenchantix in the third season, as do Stormy and Darcy. Her boyfriend was Tritannus. In Magical Adventure, Icy says she can take on one fairy with her eyes closed but Belladonna tells her to keep them closed because there are six fairies and that Bloom once took on Icy in the Season 1 finale.

Darcy: The second oldest of the trio. Darcy derives her powers from shadows and darkness. She enjoys tormenting pixies and is less aggressive than her sisters, preferring more subtle and manipulative techniques. Darcy hypnotized Riven, getting him to turn on the fairies, for most of season one. In season 2, Darkar gives Darcy a bracelet (Gloomix) that goes on the back of her hand to her elbow, which is indigo on her left hand. She has long, brown hair and light brown bangs falling through her sides and an indigo outfit with a 'D' on it, she is sometimes seen with glasses.

Stormy: The youngest of the trio, she has power over the weather, such as thunderstorms, hurricanes, tornadoes, and lightning blasts. She is the most hot-tempered of the group and is prone to violent outbursts. She enjoys tormenting both, fairies and pixies. She often does not think before she does something, which can often lead them to dangerous consequences. Stormy is Musa's rival for most of the series. In season 2, Darkar gives Stormy a bracelet (Gloomix) that goes on the back of her hand all the way up to her elbow, which is violet on her right hand. She has bluish-lavender hair styled in a cloud-shaped hairdo with light bluish-lavender colored bangs in a lightning bolt shape and a reddish-violet outfit with an 'S' on it.