Okay, my brain has had time to ruminate on secret monster thoughts, so now it's time to turn this detective into a bird. Why? Why not.
So, magic bird beast. I am thinking of blending a couple birds together to make the Bestie Form. But using Corvidae as the base bird type. (AKA birds like Magpies, Crows, and Ravens.) But obviously not 100% those, just to make it questionable.
How is he a beastie? Well there are couple ways this could have come about.
He was born that way. It's something to do with parentage. One parent was a magic bird being/monster, while the other was not. He's a mix of the two!
He a straight up birdman. He was born a magic bird, but decided he like people and wanted to live like/with them instead of staying with whatever social/familial unit he was in before.
Bless/Cursed? Either the man himself did something, one of his parents ticked off a witch/wizard and he got hit with the "Not Human" beam instead of them, or it's something generational and he's gotten the (un?)lucky roll.
Personally speaking, I can come up with scenarios for all of the above. I think, however, for this one I'm gonna lean on the "Generational Curse" option. Just to make the whole thing more interesting.
An inherited curse that shows up every couple generations, and Grimoire was the one that got smacked with it for his generation.
It was originally done to cause a monstrous transformation that turns them into rabid monsters as a punishment for doing something they shouldn't have or bc they'd made an enemy of someone with magic. One member of the family (either someone who married in or the parent of someone who got it) managed to change the nature of the curse, making more of a tool or an inconvenience instead of something that would ruin the family/person it happened to.
Grimoire has 2 forms because of it; His ordinary human face and a kind of hybrid form.
The Hybrid form is actually his default face, and he can change to the human at will. But, he can only stay in/maintain it for a couple hours at most. He has some kind of token/tool/accessory that he needs to wear/keep to hold his form for a longer period, a charm that helps him stay in the form he's in while wearing it. (And to avoid transforming in his sleep or after losing consciousness.)
Either he knows someone willing to make the charm, he has a relative who makes it for him, or it's something he knows how to make himself. If he loses it, or it gets stolen, he only has a couple hours to find it before he changes to back to his Hybrid form.
Grimoire rarely ever takes off his charm. In fact, the only time he takes it off is when he's at home and 100% sure no one is going to come visiting.
The Hyrbid form looks genuinely like a hybrid of a monster and human. Very much a bird-human. If he has wings, they're way too small to fly with or there's something wrong with the feathers to make them unusable, and he's probably too heavy to fly anyway.
Grimoire likes being a detective, and likes being around normal humans, so he doesn't really let anyone know about the curse he's long-since learned to live with.
He likes being a quirky detective with a big collection of random things in his house that people enjoy working with/having around.
Of course, to have an AU with this, his secret has to get out at some point. At the very least, Sally has to learn about it. Right?
A scholar found a leather tome one autumn afternoon,
Its pages gilt with curses old beneath October’s moon.
He bore it home with eager hands, convinced he’d found his prize—
A gateway into secret arts, forbidden, dark, and wise.
The grimoire promised mastery o’er death and fleeting time,
With incantations etched in blood, inscribed in cursive serpentine.
“Three wishes shall be granted thee,” the…
