Lilia says that “Sebek’s magic manifested rather late,” but we are not told his exact age at the time.
We see in a flashback that Sebek couldn’t “consciously” use magic until a year and a half after Silver learned how to do so. And Sebek’s use of the word “consciously” is interesting.
Are fae capable of using magic from birth, like Malleus, but Sebek’s magic was smothered by his human half, resulting in magic produced by his fae-half that he could not control until his human-half caught up? It is most intersting to think about.
(And to have such a powerful birthright that was wielded by everyone he knew denied to him by his father’s genes would explain even more about his apparent impatience with his father, but this is all speculation.)
In a vignette we learn that Sebek has yet to learn cleaning magic. His attempt to do so anyway makes a stain bigger, instead.
Sebek says that color changing magic is learned by human mages learn immediately upon entering magic schools, insinuating that he is capable of using it himself as well (he does not appreciate Ace’s joking insinuation that he can’t).
When Sebek fails to imagine himself in his dorm uniform in the dreamscape of Book 7 Ortho explains that the first-year students have only recently learned how to use magic to change outfits (Silver says he, too, has yet to master what he calls “illusion magic”).
During the Nightmare Before Christmas event Idia realizes that Sebek is magically weak, saying that he is first-year level “at very best” and he had thought that Sebek’s failing efforts to repel ghosts with his unspecified attack spells were due to poor strategizing, but “it’s actually ‘cuz you’re bad at controlling your magic, isn’t it? I can tell you’re the type that’s high output and low control. I don’t wanna hear about matters of pride from a guy who can’t or won’t openly acknowledge his own skill issue.”
Sebek responds that he knows better than anyone that he is not strong enough.
Sebek uses unspecified attack magic during Book 6 in an attempt to defend the campus against CHARON.
He uses fire magic during his fight with Lilia in Book 7, and in a chat we learn that Sebek is capable of conjuring a fire pillar. Sebek credits Lilia’s guidance for this ability.
It is visually insinuated in Sebek’s dorm uniform vignette that he uses lightning magic during a practical magic class, and he threatens to strike campus visitors with lightning outright during Halloween.
Much like Epel, Idia and Jade, Sebek imbues a plushie with magic during the Harveston event, and he uses a “binding spell” on Skully (simultaneously with Jamil) during the Nightmare Before Christmas event.
Sebek says that he does not have enough control over his magic yet to perform tasks like moving chairs. He says, “I must learn how to wield my magic more precisely as well. I constantly practice, and yet…”
Twisted Wonderland Reference Note 