Gloomix is a power-up introduced in Season 2.
Gloomix takes the form of a glowing necklace or arm cuff with a single gem on the end that assume the respective shades of the wearer. In "The Phoenix Revealed," when Darkar betrays the Trix and sends them to Oblivion, they merge together into the Mega Trix and three more Gloomix jewelry pieces that can be seen on them: a yellow hip adornment and two yellow leg bracelets.
- The name "Gloomix" is derived the word "gloom," meaning "darkness, dimness, or obscurity".
- So far, Gloomix and Disenchantix are the only witch powers/levels that are named, with Disenchantix only being named in the 4Kids dub.
- Gloomix, Disenchantix and Shape-Shifting Witch are the only Witch Forms to not make an appearance in the comics.