The Trix are the main antagonists in Seasons 1 and 6, the secondary antagonists in Seasons 2, 3 and 5 (as well as Magical Adventure), and return as the Bigger Bads and final antagonists in Season 7. They do not appear physically in season 4.
The Trix are the descendants of the Ancestral Witches (Three Ancient Witches in the 4Kids version) who destroyed Bloom's home planet, Domino (Sparks in the 4Kids version), and created Valtor (Baltor in the 4Kids version). It is debatable if the Trix are actual biological sisters or not. But they call each other sisters in some cases.
At the beginning of the first season, the Trix seemed to be more powerful than the Winx Club (with the exception of Bloom), as seen in the episode Spelled where they were able to get the better of the fight, and would have won had Bloom not intervened. For most of the first season, they attended the Cloud Tower School for Witches until they are all expelled after they created the Nightmare Monster in the episode The Nightmare Monster that failed to accomplish its purpose. The Trix stole the Dragonfire and summoned the Army of Darkness/Army of Decay to take over the realm of Magix, but Bloom defeated Icy with her dragon fire while the other Winx defeated Darcy and Stormy.
For the next two seasons they had powerful allies. After being sent to Lightrock Monastery, in the second season it was the infamous Lord Darkar who released them and gave them their Gloomix to increase their power. Darkar double-crossed the Trix in the end before he was killed and they were imprisoned in the Omega Dimension. In the third season, they joined up with Valtor and the three witches competed for his affections, before finally leaving him when he assumed his original, demon-like form and lost all the spells he had stolen when he was fighting Bloom in the 25th episode. Afterward they are sent back to Lightrock Monastery.
They returned again in the second movie, where they sneak into Alfea during the beginning of year festivities, putting a spell on all the food there so that everyone who ate some of it was turned into a toad, and stealing a magical compass which they used to lead the Ancestral Witches to the Tree of Life found in the Pixie Village. The Ancestresses proceeded to absorb all the essence of Good from the Tree, causing all good magic to disappear, and only evil magic to keep on existing. At the end of the movie, the Winx Club, the Specialists, Oritel and Erendor arrive at the haunted city of Havram to find the branch of the Tree of Life which the Ancestresses gave to the king of Eraklyon as part of the deal which forced him to help the Ancestral Witches in exchange for their sparing his kingdom. There, the Trix and their Ancestresses were waiting for them, but the Winx Club girls gained back their powers and Bloom's horse, Peg, became a flying unicorn thanks to the magical branch. Finding the Trix too weak to defeat the Winx Club, the Ancestresses try to possess the Trix, but they attempt to flee as the old witches capture them and possess their bodies. The Trix, now possessed by their ancestors, have become more powerful than ever, as well as mere puppets possessed by the Ancestral Witches. The Winx, the Specialists, Oritel and Erendor take part in the battle, but Erendor is severely wounded trying to save Bloom from Icy-Belladone. Finally, using a Believix convergence, the Winx Club are able to summon the essence of the Great Dragon and extract the Ancestresses from the bodies of the Trix. The Great Dragon's power destroys the Ancestral Witches for good, and the Trix, defeated, fall unconscious to the ground. Helia ties them with a rope and, as the movie ends, they are shown as being suspended from the flying ship the Winx, the Specialists, Oritel and Erendor use to leave Havram, getting angry as Bloom and her fiends fly around them and tease them.
- As Season 3 is the final season of the 4Kids version, and Season 4 (in which they are not present) is the final season of the RAI English version, in both versions the Trix's final fate is to be imprisoned at Lightrock. Any returns after are exclusive to the Italian and Nickelodeon versions.
- The Trix may have been partly inspired by Hydia, Reeka, and Draggle from G1 of My Little Pony, who are three witches who love everything to be dark and gloomy (though this is more apparent in the 4Kids version). The Army of Darkness could be a counterpart to the Smooze, while likely being named after the Evil Dead film of the same name, and being raised by a book similar to the Necronomicon (though it is called the Army of Decay in the 4Kids version).
- The Trix were most directly inspired by Bellatrix Lestrange: They are both sadistic witches, their outfits are similar, and their love for Valtor can be compared to Bellatrix's love for Valtor's inspiration, Lord Voldemort. Also, the name "Trix" is the last four letters in Bellatrix's name.
- They share their name with a cereal, although their name is likely more intended to resemble the word "Tricks" combined with names of transformations or powers often ending in "ix".
- They are the only main villains to physically appear in more than one season and they've had a large impact on the series, plus they're the arch-enemies of the Winx Club; consequently, they are the overall main antagonists of the franchise. All other main villains died in their respective season except Tritannus and Acheron, who are both imprisoned (though Tritannus returns in one movie).
- The Trix are the same as The Dazzlings from EG Rainbow Rocks The Wubb girlz from Wow wow Wubbzy The Powerpuff Girlz And The Cutemarks Crusaders from My Little Pony