Sorcerer of the State, Thirteen.
Episode 5 of Zero Kara Hajimeru Mahou no Sho (Grimoire of Zero) is out and begins with the trio stumbling into the town to find that people are dead by the dozens, with Mercenary noting that not even bandits go this wild. Then they find one who has a choker like Albus and Zero becomes sure its a witch’s doing that caused this, identifying the magic used to cause the destruction and being upset because she never intended for magic to be used for such things.
When questioned on why the town, which was harboring witches in the first place, was attacked, Albus states there’s more than one group at play. These rogue witches are those turned down by the Sorcerers of Zero and wantonly attack anyone, adding to the bad name witches have. Albus figures that they came to steal the grimoire, but then they bring up a point when it comes to asking who killed them in turn.
That’s when Albus nearly gets attacked by an arrow and is saved by the dog from last episode. It turns out to be looters, so Mercenary goes to deal with them. Afterwards they decide to send the dog off to the town where the children were before they go out to deal with the guy responsible for this. Inside of the Church they find that grimoire is missing and believe that Sorena’s granddaughter took it, only for a survivor to reveal that the man mentioned before had some mysterious way of killing his assailants before dying.
As they head out, Zero and Mercenary reason that there were more than one assailants. Albus suspects its Thirteen, but uttering that name causes a forced summoning that drags them down into a dark place. Mercenary falls into a bad memory where he slaughtered people using him, but Zero breaks him out of the spell and confirms that only two people know it, one being her teacher, Thirteen.
Thirteen questions why Zero left the caves, before Albus reveals that he’s the Sorcerer of the State. Albus considers him a traitor, which is more or less proven when it turns out that when the Sorcerers of Zero approached the king to ask him to stop the witch-hunts, he basically agrees to silence them in exchange for help finding the grimoire.
He also seems to have something against Zero, as he attacks her and Mercenary. Zero gets pissed and it leads to a magic duel between them, believing that he crossed the line by turning against the other witches. And there the episode ends.
So this episode gives us more depth into the whole affairs, revealing that Thirteen had sided with the King in both an effort to reclaim the grimoire and that he hates Zero’s name being thrown around so casually. It’s clear that the student has surpassed the master at this point, but his wanton and causal dismissal of life is especially jarring compared to Zero, leaving you to wonder just how they got along in the first place.