I think the similarity between Malleus and Grim might be because Grim is Malenoa's phantom.
To preface, I'm assuming Malenoa overblotted because of the scene in Sleeping Beauty where she snapped at seeing Diablo turned into stone?
Additionally, both movies of Maleficent involved a "death scene." In Maleficent 1, it was Diaval being chained down by King Stefan's soldiers/Maleficent was about to be slain by King Stefan and in Maleficent 2, its Maleficent actually died from protecting Aurora.
Both scenes eventually had a "saving from their impending death." But, since this is twisted wonderland, the Disney movie is more inspired by the Original Animation where Maleficent and her goons actually lost to the humans.
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Diablo (Maleficent's birb) in TWST, is Levan right now and in recent updates its said that the latest news about Levan is that he's missing and there's rumors about him fighting Knight of Dawn; the strongest of the Silver Owls.
Right now, the Silver Owls are ambushing the Land of Briar castle where Malenoa is.
If it goes like this??? I think they kept Levan as hostage to officially take the land or something—
All I know is that someone must've harmed Levan because in the movie, Maleficent only attacked the kingdom or used all her powers to kill Prince Philip upon discovering the fairies turned Diablo into a stone bcs they want Prince Philip to escape and save Aurora.
From the words of Lilia about Malenoa, Malenoa is undefeatable– so I really don't believe she was overpowered by strength, but rather she was caught off guard by emotional turmoil (or for this theory, consumed by her own overblot).
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Going back to Grim might be Malenoa's phantom… Grim is always assumed to be a phantom labeled as a direbeast for now... Its heavily theorized like that because of how, in his feral state, he devours blotted magic stones.
And, blotted magic stones are what supplies a phantom to live because they carry the magic power of a mage.
But phantoms can't be born without an overblot first... so who's mage is he a phantom of?
We know that the phantom's strength is a reflection of a mage capabilities when they were at the right state–
Malenoa was a really powerful mage so if we consider the destruction of NRC (and possibly the Sage Island? The entire sky was black out too) that we've seen in the prologue as the power of Phantom Grim, then Phantom Grim must originate from a formidable mage like Malenoa, because he easily beaten all mages on the island effortlessly and even plunged the surroundings in darkness.
If Grim is a phantom then he's a powerful one because he's ancient (assumed from his diagnosed curse from STYX), he has the intelligence of a human, and has immense destruction power (if he's not sane as shown with how he easily destroyed his cage room at STYX).
Also even if Overblot Grim is composed of different parts from the main 7 phantoms, his form is majorly resembling a dragon. And, Malenoa's a dragon.
(long post ahead)