Charisma, or perhaps it should be called presence.
People instinctively gauge others' presence.
There are several criteria for measuring how heavy that presence is.
How large someone's physique is and how beautifully they're made are important.
Or things like having an amazing bass voice, or wearing clothes from a very expensive boutique can also have an influence.
The position they hold is of course important too.
Obern Grimoire that students see.
He exuded charisma in all those aspects.
Even students from prestigious families, and even the arrogant prince could feel it.
You could tell by how silence fell instantly at his appearance.
But Obern Grimoire's charisma wasn't just about external aspects.
His actions and words have no hesitation. He seems to fear neither nobles nor royalty.
What could he trust to be able to do that?
Perhaps, his magic.