If the overall Lovecraftian Mythos would most likely be Magic (uncaring, aloof, alien, weird), would a Mythic Europe version of the Deep Ones (let's use the Arabic word 'Amiq say, because it sounds... well it just sounds cool) also be Magic aligned or could a Faerie element (bargains, exotic blood traits, partly human appearance) be combined into the mix? Or something different entirely?
Partially human appearance does not mean Faerie. Deep ones are interested in being left alone AFAIK. They can interbreed with humans, though. I would still put them as magic. Using the atlantean profile for starters could work. Magical humans and all that. Dagon is adored, but nowhere does it say that he cares the least about such adoration in the surface. For the Deep ones underwater he is simply Da Boss, so they show him respect.
I was reading a lot of Mythos related material at the time... I even thought of as representing a shoggoth as a "Flesh Elemental" using Elementalist magic.
Clearly a dark and warped time in my life...
Thanks for all the comments - I think Faerie works best (although magic Kin could work) but the original Abgal would be interesting in themselves.