Where do I get Charcoal for a certain quest?

I'm fairly confused as to what drops it as well. Nothing in my bestiary lists it so far

I've gotten that drop while doing Odin's dungeon. I'll edit this post with the mobs name when I can find it xD. Edit: Alright this a picture of the boss, basically a different version of the ones you see in earlier dungeons. Can't really recall if their in other dungeons besides Odin's. Sorry :/.

Hrm. If it drops from them, it might also be a Murikabe drop as well

This thread says that it drops from Dainurikabe and Akamekabe. No idea on their location, though (seems like they're Kyoto-based from two posts above me).