- Previous Transformation: Standard Witch Form
- Next Transformation: Disenchantix
The Gloomix takes the form of a glowing necklace or wrist cuff with a single gem on the end. The Trix receive the Gloomix from Darkar, and use it. So far, the only known witches to earn this are Icy, Darcy, and Stormy.
At the end of Season 2, when Darkar betrays the Trix and sends them to Oblivion, they merge together into the Mega Trix and three more Gloomix can be seen on them: a yellow zone and two green leg bracelets.
Gloomix is the witch version of Charmix, given to them by Darkar and it makes them more powerful. However, while the Fairies obtain their Charmix naturally as the second level of their magical progress, it has not been precised whether other witches can also have a Gloomix or if only Darkar can give one to a witch.
Shortly after Darkar's defeat (possibly within a week, since the end of year party occurred in the last episode of Season 2, and the Winx were already packing for vacations in the first episode of Season 3), the Trix were captured in Relix by the authorities of Magix and sent into the Omega Dimension, and the Gloomix had completely disappeared, perhaps since Darkar, who had created them, had been defeated.
- The name Gloomix comes from the word "gloom", which means darkness, dimness or obscurity.
- Gloomix can only be used with the accessories Darkar gave the Trix.