My guess is that the boss is related to primordial dragon bones that become dinosaur bones when named... So maybe it's a dragon-dino chimera or something. Maybe wonder stones are prism shaped because of the dragon-rainbow relationship.
Read that youkai also meant strange bird/fire. So somehow dragon=dino=bird maybe... Could be a lot of things, also seen some post talking about Kojiki as well as Ainu religion and many more...
Izanami whose design could be bone related and is someone sealed underground since ancient times.

>>49792008
Would be funny and could mix well with youkai if it really was used for birds... The kanji nue was also originally used for a bird as well.
Guess the design might look like an undead bird or similar if it's something like that.

>>49790431
Some Futaba post also mentioned Quetzalcoatl and I guess we have technically el Dorado in a song title... but I doubt we get some native American gods... maybe via synchretism it also being the dragon god and the Hong and so on...

>>49790313
Thanks, way easier to see like this.
Also saw someone saying that the "tail" at the left might be a massive ponytail.
But I guess the "bonetail" might as well just be a fossil that the 2hu is holding, rather than a part of her body.