Spoiler!!! but Kamui is niether Hosidan or Norhian, you find all this out in Revelation, he bears the power of Anankos and his ability to turn into a dragon must be something that only the Vallite royalty can do, that being said that would mean that Aqua would have that ability as well, which does not seem to be the case. In terms of Grima, he is not a divine dragon but actually the creation of a mage from Thabes. The mage who's name slips my mind at the moment dreamed of creating a singular perfect being, and Grima was the result. The mage ended up being the first of the fell bloodline as well. You find all this out in Shadows of Valentia.
