Alright well I think the first argument I'd make is that he's on the Senior Council. I think that after all this time they would have figured out he was not a mortal wizard. One of the big reasons for this is only mortal wizard can do certain kinds of magic, or at least that's the rules that have been laid out to us. I don't think he'd be allowed to be a member if he was not an actual wizard. No one else like Mab, or the Mothers, or Angels or anyone sits on the Senior Council except mortal wizards.
And on the grey council either, but we already have one God/mortal on it, Odin. Wizardy is the required element and a mantle does not unmake a wizard. Odin manages both and GK's the next archetype over from Odin, He's Horus, more or less, in Origin. The Moon being his domain is the biggest indicator I remember on why... but we've previously hashed this out here at one point. I don't see a purely mortal nothing have a domain of their own(which is to say a place that they sync to exactly, Like Odin and Norway) that's gotten to by walking across the surface of the moon... NOW a moon god though....
"The faceless god", "The messenger of the Outer gods", "The Crawling chaos"....The list goes on. Here is how the story goes when he was a Pharaoh: https://www.youtube.com/watch?v=W1rm9KRBg7g
Mother Winter I guess could be an Outer god, but what indication is there besides her sunny disposition?
Besides MS telling her it's not her world, power level. She's a F'n beast in power? Various other reasonings, but most of what I theorize is springboarded off of what I consider other viable theory, Like MW is basically the embodiment of DR. The Traveling Stone next to her cottage is actually the lighthouse entrance, hence it leading to the Outer Gates. Also why it's originally put in as HERS and not theirs, MS just stays there by proxy. She's not Death so much as The End, of all things. Those forgotten become nothing more than an aspect of her Masks.(Lady Night, Nyx, the Darkness,
oblivion conceptualized). An those things insider her waiting to get out? It's like the mental battles in GS, except she broke off a portion of herself, gave it leverage, to fight against the things struggling to get out.(your not immune to yourself, after all) If you want to get into the Lore, DR is the
reason she's crippled, each hall represents one of her ankles, knee's, hips, shoulders, elbows and hands, respectively.