Reading these chapters, this give me nostalgic feels, this felt a lot like Lullaby arc. With the final boss being not human.
Is Avatar is weaker than Eisenwald or is Fairy Tail just that much stronger than they were back than. Maybe a little bit of both.
What Arlock did betraying his comrades and was actually planning to kill them as well as himself was duchy, but in a way I think they had it coming, these people were as far as they knew willing to kill innocent people, so they deserve it.
Ikusatsungai does look beast I give them that, but it is Lullaby 2.0