So, the 2 big things I wanted to do with this transformation were 1) make it an actual mermaid form because that just Makes Sense imo, and 2) combine the aesthetics of Sirenix and Harmonix into one form, for the sake of mostly my own sanity. Design-wise I mostly pulled from Harmonix (I really like the flowy, more elegant elements of the form, and I thought turning the ribbons on the shoes into arm accessories could be cool), but I also took a few things from Sirenix, notably the dyed hair streaks and some hairstyles (while I don't like the colours they chose for the underwater hairstyles I like the concept, so).

Some of my favourite details are the wings and tails (which are supposed to mimic each other shape-wise, except in Tecna's case because I decided her being an eel was a fun idea since. well. electric eels) and the styles of the tops, which I started doing to incorporate more obvious "ocean" vibes as well as the asymmetrical designs of the tops in both the og transformations.

(I'm also particularly proud of Aisha's hair ngl, genuinely my favourite design out of anyone hairstyle. I wanted smth that wasn't just another ponytail and saw an opportunity w goddess braids and ran).

ANYWAY lore time !!

So in my version of Sirenix, it was an ancient transformation crafted in collaboration with the mermaid-folk on Andros, at a time when things in the Magic Dimension were far more dangerous. It was created to help better defend the Infinite Ocean, along with the various other oceans of the different realms/planets in the Magic Dimension.

In order to ensure the form could not be accessed by those who might use it for ill, access to it was heavily guarded. A fairy who wishes to earn it must complete a quest in which they find 3 gems (one of Courage, one of Empathy, and one of Kindness) and present them to the current Guardian of the Source of Sirenix (at the entrance to the Infinite Ocean). They must also detail their reasons for requiring the form, and access to the Infinite Ocean, and only if the Guardian is pleased with their answers will the power be granted.

Unfortunately, as of the time in which the Winx would go on this quest, Sirenix had been cursed. Politea, one of the nymphs guarding the source, betrayed her fellow guardians to side with the Ancestral Witches. When they ran out of uses for her, they cursed her, transforming her into a horrid sea monster, and rendering traditional access to the power impossible.

(Until the events of season 5 of course but that's a story for ANOTHER DAY-)

ALSO. Sirenix CAN be used out of water. But it's much weaker (think of like. how penguins are kinda clumsy on land but are super graceful in the water. Sirenix is like that). It does have a specific form for this that I am still working on but did a rough sketch of to show the concept: