Also it has been marinating in the effluvia at the foundations of the Thousand Hells for who knows how many ages of the world. If it were anything but that it is it would have long since been irrevocably claimed by that place. Instead it now empowers its bearer with the stolen lore and mirrored powers of hell.
That's an Exaltation for you!
Anyway, I've been doing some thinking on the matter,
really doing some thinking, and I think I've hitched upon the right
Aesthetic for Shintai Form.
It's Molly's True Form, her manifestation of Ultimate Strength, the Ideal that she seeks to embody, influenced of course by infernal themes of course but
the core functionality is the same. We're not looking at a rag-picker, or something excessively eldritch, because those aren't what Molly thinks about when she envisions Strength.
Papa Carpenter is Strength as far as she's concerned, and he's a sword wielding, literal White Knight dropped into a complex world with the ability to make everything simple. That's her oldest interpretation of Strength, and that's probably going to have a large influence on what her Shintai looks like. The Sword is a
start, because in a sense, it's her trying to ape the Sword of the Cross, but she's probably going to have some fancy form of armor going on.
Then of course, there's Dresden, mister Super Wizard Himself, who's one of the Wise--who uses his power to make things a little bit better for everyone instead of hide in his bunker and do Very Important Things that nobody actually gets to know about because they're just too plebian to care. He casts spells and doesn't afraid of anything, and he makes Magic something
good instead of something that just exists except when it's causing problems.
Then, of course, you've got to feed all of this through a blender that is a genuinely faithful upbringing, her love for pop culture and latent nerd energies, and her like for gothic architecture and aesthetics. Add infernal themes as spice, and you've got all the pieces to create a flavorful Shintai that actually matches Molly's history, personality, and everything else.
So, what do we get out of that?
Probably some super anime-as-fuck cross between Sauron, probably get one of those wild Asura's Wrath halo mandala things characters in it manifest when they're going All In, and slight hints of a more mystic nature that carry through with the eye.
Of course, I don't really know how to piece this together, because I can't really hold a picture in my head, but the
words feel right.
EDIT: Maybe use Mordred's armor (From Fate) as a baseline and tailor it up to fit? That seems to hit that wiggle room between knightly armor and supervillain aesthetic that you can attach the other details on.