The concept for this design was cobbled together from a bunch of somewhat related things, but the two most important components here are
Melusine, a European female water spirit with draconic qualities, and the
hagfish, an extremely basal jawless vertebrate which secretes massive amounts of slime in self-defense and to maneuver through tight spaces. Melusine's myth is heavily steeped in tragedy and broken promises, and in more than one telling, it ends in the death of the one who fell in love with her beautiful human disguise only to wrong her by seeing her true form... via a mysterious poisoning. Initially I wasn't actually going to include the hagfish aspect and there wasn't even going to be a slime coating at all because it was planned to be a reptile of some sort, but
Golurkyourself made the neat suggestion of giving it an oil slick motif in order to justify the Poison type better (without that, it looked more like a Water-type). The hagfish barbels were added literally at the last minute but I'm glad I included them, even if they kinda detract from the "waifumon" aesthetic I was going for initially. Oh well.
Anyway, the pitch I had in my head for this design was a peculiar, slimy water monster that tries to hide its (from its own perspective) repulsive true appearance behind a more regal-looking façade; I suppose any one of the priority-negating abilities could've worked with that concept, but I ultimately designed it with
Queenly Majesty in mind. Flavor-wise, the story goes that once upon a time, this mysterious, elusive creature was extremely beautiful, gentle, and kind, yet utterly naïve. In local legends it was seen as a spirit of nature, a caretaker of the world's waters and all life calling them home, and a major source of artistic inspiration. But when its home became blighted by manmade pollutants, it was forced to draw the poisons out of its habitat and store them inside its body, corrupting its nature and ruining its innocence forever. Now it scavenges trash and litter in the vain hope of restoring itself to its original beauty, namely by scraping together a covering over its actual body that's held together by the mucus it secretes. Thanks to the toxins it absorbed, said mucus is now oily, sticky, putrid, and as poisoned as its mind, consumed by vengeance and bitterness as mankind's callousness towards nature and the encroachment of civilization upon what little is left of its wild refuge forces it to lash out savagely.
Since Melusine is associated with mermaids and those in turn are known for singing, that alone could justify Clangorous Soul, but I decided to add in some flavor context for Clanging Scales as well, and after some thinking, I decided to turn the hair-wings of this design into a cross between wind chimes and a glockenspiel. Before its corruption, the creature would've basked on riverbanks and let the breeze make the ornaments in its hair clink together to make a beautiful sound produced by nature, but now it rattles its wings to harshly clang these now-metallicized ornaments together, making a terrible racket to ward off those who see it in its true form. In battle, it can also "play" these ornaments using its forked tail - referring to a feature commonly ascribed to Melusine herself, namely two mermaid or serpent tails. By arching its tail back and striking its wing-ornaments with the two scorpion-like stingers on its end, it can create a melody of clanging sounds to accompany its song-like vocalizations, a harsh and haunting testament to the misery it endured. To add to the music theme, the forked tail tips also form a treble clef when coiled, while the wings have bass clef decor and half note ornaments, and a marking on the chest armor invokes both a crude skull pattern and a whole note. Finally, the headpiece is styled like a
French hood, as seen on many portraits of French duchesses in ages past - Melusine is most associated with France, though her myth has found its way throughout most of mainland Europe in one form or another.