Theory I have:
We know each island has it's own Deity Guardian and I'm willing to bet that they have the same types as the Kahuna, as we know that Hala is the Melemele Kahuna and Tapu Koko is the Melemele Guardian (Tapu Koko was also seen under Hala's control). This might also mean that Sophocles is the Melemele Trial Captain, since he fits with the Electric theme.
So from this, I'm inferring that we're getting a regional quartet of fairies: Electric/Fairy, Water/Fairy, Grass/Fairy and Fire/Fairy.
We know each island has it's own Deity Guardian and I'm willing to bet that they have the same types as the Kahuna, as we know that Hala is the Melemele Kahuna and Tapu Koko is the Melemele Guardian (Tapu Koko was also seen under Hala's control). This might also mean that Sophocles is the Melemele Trial Captain, since he fits with the Electric theme.
So from this, I'm inferring that we're getting a regional quartet of fairies: Electric/Fairy, Water/Fairy, Grass/Fairy and Fire/Fairy.