It wasn't until today that I noticed the "an undine spirit" mobs inside the building, looking up into an attic space. They are yellow wisps and I got a crown from one of them. In case you're struggling to get your crown, check for these!
I wiped the island, and after many deaths, I can say they are definately NOT common. None of the various drakes, nor the sphinixes. So unless I did something wrong or got very bad RNG the rarity needs to change. 18 mobs I'd say and no crown.
I was on a raid in pos made it to the 6th island and im a mage!!! the bee boss thats there was bugged and was flying off the island so we couldnt go to the 7th island! that really stinks!