So much potential, all down the drain in the first episode.
In the first episode, the viewer is led to belieave that the show will be about the relationship and adventure of Mercenary - a beastfallen and Zero - a genius witch, Zero even summons an cute demon, but guess how many times demons are summoned after this? 0, but time after time I kept thinking what does this story want/try to be?
This is why light novels and their adaptations are not taken seriously, the story is too convenient = things and events happen or are fererenced right before they are needed, full of plot holes that are sloppily fixed later...
Imagine playing an rpg and getting into a room full of traps and suddenly an old man emerges from the shadows and says that the room on the left has an item that reveals all the traps, and later it's revealed that the old man was actually a ghost who died to the traps and was there to prevent the same fate from falling on others.
There is an actual fricking "Arrow to the knee" line... sigh
Were you hoping for a satisfying conclusion and after math of removing magic? Too bad for you, that would be good writing.
Thoughts
Story is average, so much potential and interesting ideas... none of them properly explored.
Great animation, althought mostly just people talking to each other.
Sound is great and fitting.
Characters are average, the show is more interested in the story than in developing the characters.
About the Magic
The magic is very inconsistent, there are two magic systems, a ritual and magic circle based one and another one that needs neither.
The ritual magic exists and that's basically how much we see and learn about it, the new magic system is created, not developed, CREATED by Zero and she can deny said magic when others use it, but only sometimes, oh and how was she able to create magic? Demons... she made a deal with a demon who patrons the magic...
Sometimes the new magic needs incantations, the chapter and page number said out loud and sometimes it doesn't
About the writing
Way too predictable narrative, when the party is nearing Latette they put up all the death flags available, HIM is exactly who you think he is, Brats reaction to the grand daughter of Sorena is way too obvious.
Characters are not consistent, 13 stops his plan in a snap , Zero says 13 crossed the line and it's unforgivable and then proceeds to go eat lunch with him...
Hordem keeps and abuses slaves and later it's revealed that he is actually a good guy tasked with protecting the grand daughter.
HIM is constantly said to have the grimoire, but at the same time they wonder who has the grimoire and at times they say a Sorcerer of Zero member must have taken it.
A random witch says that only the creator of the new magic system can seal it, how does she know this? Oh and later Zero says that she needs 13 to help her seal the magic but only when they are already ready to seal it, oh and then they say that they need a third witch and the Brat comes, oh and then Zero says that now they need a offering of greatest quality...
Oh and obviously Zero wrote the spells with intentional mistakes to always have an advantage against other witches, even though she created the magic not for combat but to help everyday life, oh and this is not apparent or referenced before the fight between Zero and 13...
Oh and the plague was started by novice witches, but if you thought that you would find out why or who the witches were, you clearly haven't seen LN shows before.