Thank you so much for your kind words!! I definitely do not think I know a lot about the characters (I originally started the character facts project because I have a poor short-term memory and wanted reference sheets just for me), but I really appreciate the kindness ♡

I have come across some theories on accident but I usually avoid them because sometimes people are correct, which can be so amazing, but then I have spoiled myself!

But this was a great opportunity to look into what is out there at the moment and these are my top four favorites (no Book 7 spoilers): (disclaimer: none of these theories are of my own creation!)

Theory #4: Ruggie was supposed to overblot in Book 2, but Leona intentionally took over his blot to spare him.

In Favor: Ruggie used a lot of magic throughout Book 2, culminating in a potion from Azul for Ruggie to overclock himself and overcome his own magical limitations, which seems like it should be a big deal for blot accumulation.

But he never seems to suffer any consequences to his physical or mental health while Leona, one of the most objectively powerful characters in the game, overblots after using his unique magic just once (and we see him use King’s Roar a lot more during Book 6 in much more physically challenging conditions while being limited by the blot escaping the Underworld and using the thunder spear three times, twice by himself while Riddle and Vil both received help).

This would tie into the theory that 1) there is a time loop happening where everyone is reliving the same incidents over and over again and 2) Leona is aware of the loop to some degree (re: Idia’s “Leona’s probably the kind of guy who always knows he’s dreaming”): Leona may have already experienced a scenario where Ruggie overblotted and has been taking on Ruggie’s blot in every loop since in order to keep it from happening again.

Looking at Ruggie’s backstory, all the effort he put into Book 2 and why, and how badly he was hurt when Leona crushed his dreams, Ruggie has just as much trauma and uses just as much magic (if not more, since his gets superficially enhanced) than any of the others, and using their unique magics on too many people at once is exactly what lead to overblot for Riddle, Azul and Jamil. (Credit for this theory to this person on Yahoo! Answers: https://detail.chiebukuro.yahoo.co.jp/qa/question_detail/q13231307863 )

Against: Looking at the timing of the blot animations they only appear after Leona has gone through something emotionally taxing, regardless of whether or not Ruggie has been using magic (an animation appears after Ruggie trips someone down the stairs in the beginning, but no magic precedes the 2nd or 3rd animations and the 4th is after King’s Roar), so it is definitely Leona’s blot. This doesn’t mean that he isn’t also accumulating Ruggie’s blot, but if we’re basing things on what is happening on-screen, then this theory is a little weak.

Theory #3: Rook is a bird beastman. Credit to @MoonlightEquin1 (who is amazing) for this theory! https://twitter.com/MoonlightEquin1/status/1625355253951664128?s=20

In Favor: Just to reiterate the content of the thread, Kifaji is our first look at what a confirmed bird-beast-person looks like, and that is: a lot like a non-beast-person.

We know Rook is also from Sunset Savanna (and, as mentioned in the thread, a rook is a type of bird) and he has unusually excellent eyesight, even getting called "eagle-eyed".

Lilia says he has “good eyesight for a human,” but the fae characters all refer to anyone who is not also fae as “human” or “children of men,” including Azul and Leona.

Rook has the line “I am a man” on NA but not on JP; it was added to his dialogue in the NA adaptation and is not something he has ever actually said.

Rook is also big on hunting, mostly focusing on the school’s beastpeople but also the humans, mermaids, ghosts and Malleus.

He also likes archery, which may be a reference to Disney’s Robin Hood (where the titular character wins an archery contest by dressing up like a bird).

Rather than assigning a fish-based name to Rook as he does for most of the other students, Floyd refers to him as “Seagull.”

A quick google search says there are eagles who will attack lion cubs and, while perhaps a stretch, there are also birds such as magpies and crows who are attracted to shiny objects, and Vil will occasionally fill the room he is in with sparkles.

Against: No real strong arguments against this one yet, and there is this great thread comparing Rook to Tarzan (not an argument against the bird theory! It is clear that many Twst characters are combinations of multiple different sources rather than being literal, 1-to-1 recreations of a single person or thing).
https://twitter.com/yoyovoyovoyo/status/1461574344136478724?s=20&t=c5u0hBvaKVRy6QHeRpoElA

Theory #2: Crowley is Malleus

In Favor: I like this one because it makes me laugh. We get a direct comparison between the two during Halloween when Crowley physically restrains Malleus from blowing up the campus, and there are obvious physical differences (besides their heights—Crowley is only 185cm while Malleus is 202, with horns) such as skin tone and ear shape, but we have seen Malleus control the weather, return Vil’s youth and many other things, while even Cater is capable of making a clone. It seems like disguising himself from himself would be a small task for one of the world's top mages, and it would explain why Crowley is consistently forgetting to invite Malleus to meetings: as far as he is concerned, he is already there.

(Credit for this theory to this three-year-old Reddit thread: https://www.reddit.com/r/TwistedWonderland/comments/i41en8/twisted_wonderland_theory/ )

Against: The two sprites share poses, there is the tropical shirt (not the same shirt but it sets a precedent), Crowley always wearing a hat…the main problem with this theory is that it seems too obvious, like a misdirect to distract from whatever is actually going on.

In Crowley’s introduction he says he has been entrusted with the school by its chairman. This chairman may actually be Malleus (which is a trick that Yana has pulled before, in her manga), so Crowley may be following his orders like Diablo obeying Maleficent in Sleeping Beauty.

1 Favorite Theory: Grim is twisted from Dinah.

This is my favorite for being so obvious that I have never stopped feeling stupid for not making the connection.