People: Shapeshifters
I've been working on this a bit since Circe's been living in my head. If anyone else has other insights that would be cool.

In Linoa island slang; a shapeshifter is a dodge (dodging from one form to the next; that's some dodgy magic) or a slider (sliding from one form to another).

There are a few different types of shape-shifters. Some shift into inanimate objects (and this has drawbacks because you start to lose your sense of self if you stay in object form for too long). Some shift into animals (similar drawbacks in that you start to act as those animals and can permanently take on their instincts and/or certain behaviors even when you shift back into yourself). Lastly, some shift into other personas (or faces).

Circe is a persona shifter, so this is the one I've learned (or invented) the most about. This sort of shifting (as most shifting that's done) alters the whole body as well as their personality. The shifter takes on another person's body, be it a body they have seen or a body they have imagined. The drawback to persona shifters is that they must have strong boundaries between their personas. Regardless, most persona shifters are a touch crazy (if not completely so). They often exhibit symptoms of dissociative identity disorder. If they are not careful they can lose their original persona. They may have any number of personas that they use for different purposes/reasons. They may use a persona for some portion of their lifetime and then discard it permanently or use it again later. Persona shifters have a sense of their original self regardless of what persona they are in and will act in the best interest of the original (barring the few instances when a shifter remains in one persona for too long and loses that sense of their original self, as in the case of Amaterasu).

Most shape-shifters live on Linoa island. Many of them also have iron and fire elements; this has something to do with Linoa being a volcanic island, fire and iron are particularly suited to living there and dealing with an actively volcanic setting. Shape-shifting is one of those types of magic that is secretive.

The shape-shifter culture on Linoa island is also highly secretive. If they don't like you, for any reason, they will kick you off their island and bar you from ever returning (with spells or simply by threatening). The secret of their existence is spellbound and heavily guarded. As an added precaution they do not allow shape-shifters under a certain age to leave the island, partially because one must reach a certain level of maturity so as not to shift into inappropriate objects or people.