Based on Magica De Spell from the Ducktales reboot that begun in 2017, here's my first truly villainous OC for Twisted Wonderland, with the reference sheet made by the amazing @MirisArt on Twitter.
Now some info about him:

Name: Gregorio
Surname: Encanto
Gender: Male
Age: 42 in his adult form; 16 in his younger form.
Birthday: April 1st
Birthplace: Land of Pyroxene
Height: 6,069 feet or 1,85m in adult form; 5,41 feet or 1,65m in younger form.
Weight: 75Kg in adult form; 60Kg in younger form.
School Role: Ex-Teacher of Ancient Curses and Conjuration and now Diasomnia student.
School Year: First Year

Personality: When you lose who means everything for you, only insanity will lead your path through life. That's what can describe Gregorio's cracked mind: after he lost the only person he truly cared about, his younger brother Noél, his psyche turned into a cauldron of hate and suffering. He can look like a calm person, haugty, always self-confident, and open to dialogue, but that is only one of the many masks the ex-teacher wears: in reality, he's a person driven by anger and madness, an egoist person who turned the love for his sibling into a possessive relationship, not accepting the fact of being left alone, and so being ready to give into murderous instincts to take Noél back from the dead and reclaim who he lost. He's an able manipulator, a patient schemer who is able to wait and study what is around himself to reach his own goal, and who, even standing before the person he hates the most, the cause of his loss, Dire Crowley, is able to not give in to the emotions, all for the sake of his revenge.
When in his younger form, to infiltrate the school and scheme his revenge, taking the name of "Felix Sinistro", Gregorio puts on another mask: he looks like a cheerful and friendly guy, open to learn and more than happy to do so and even to help others, even if being sometimes clumsy; he created a naive and a bit coward persona, a character that totally deviates from his true personality, to not create suspects in who knows his real self (the other teachers and Crowley), and to befriend other students, in order to study them and see who can be a potential threat for his plan.
Essentially a true villain, who would do anything in his power, stepping on everyone else, to achieve his own insane goal.

Unique Magic Name: "Shadow War"
Unique Magic Effect: Gregorio's Unique Magic lets him control the shadows in two principal ways: the ex-teacher can move the shadows around himself, giving them different shapes from their original, and making them tangible too, to the point he can give physical form to those, and so being able to use them both in and out of an eventual battle. Other than this, Gregorio has a certain degree of control over his own shadow too: he can separate it from himself, the shadow itself being sentient in this state even if under the wizard's control, and can even shape it to mimick his own appearance, turning it into a perfect copy totally under his control.
"Shadow War", being so tied both with the element of darkness, and with Gregorio's mana, regulates too the strenght of his spells: the power that the ex-teacher can use is dictated by the cycle of night and day; during day hours, the peak of this being at noon, the magic of Gregorio is weakened, making him perform weaker spells, while instead, during night hours, the peak of this being at midnight, the magic of the false students is greatly powered up, letting him perform stronger spells.
The maximum of magical strenght he can get is during eclipses, the moment during the day in which the darkness obscures the light, and thus giving him enough power to virtually perform any spell he desires.