[ quinn's use of his given name comes from rebekah's own use of it. she's been exposed to klaus via rebekah talking to her about him prior to his arrival, the sister always referring to the brother as "niklaus" or "nik." in her mind, she's being polite by using his given name instead of assuming she has the right to use a nickname that might be for family only. ]
I'm familiar with some of the tales of Baba Yaga and Koschei. [ via some literature courses and encountering variants of the tales in televised media over the years. (thanks, reading rainbow.) ]