Arthur is just... Arthur.
A man who would rather be anywhere that isn't here.
He is around 5"10, messy dark brown hair and a careful clipped beard and moustache. Dressed in old leather gear he would look the very picture of a down on his luck adventurer.
Around his neck he wears a wide, heavy res scarf with blue and yellow stripes on the ends. Beneath this scarf, Arthur hides very primitive looking gills.
Dredge... is Dredge.
A primordial creature of the deep who's contributions to the world can be defined as unhelpful at best and seriously problematic at worst.
Dredge has chosen Arthur to be his host for the simple fact that Arthur simply couldn't be bothered to fight him off.