I'm wondering if we'll soon find out more about Cartaphilus' backstory.
Spoiler for Speculation about Cartaphilus:
From the hints dropped in Chapter 37 it seems Cartaphilus is made up of two people: one of whom is a boy whose body Cartaphillus is currently inhabiting. I wanna say this boy (who looks like he was a mage of some sort) was also the one who took Chise's hand in Chapter 31 and gave her her wand. It'll remain to be seen if this is in fact true, but my current guess is that this mage (whose name might be Joseph) allowed Cartaphilus to inhabit his body, as Cartaphilus' original body was decayed but due to his curse, Cartaphilus could not actually die, and lived in constant agony. However, even with the body swap Joseph's body inherited Caraphilus' curse and so the Cartaphilus we now know went on to use magic to find a body that would overcome the curse (how exactly, I don't have an idea yet, but all the experimentation on other fae and humans seen to support he's after something).
Based on the few scans of Chapter 41 posted online, it seems like Cartaphilus exchanged eyeballs with Chise (this is going to be so squirk worthy when it gets animated D
. I'm not sure what his goal for that is, but it's somehow allowing Chise to see her mother.