Who is Sergei from Enchantment and what is their importance?

Sergei is Father Lukas' scribe, but he feels as though Father Lukas uses him more as a slave than a scribe. Sergei befriends Ivan when he comes to Taina and writes down the many fairy tales of his people at Ivan's urging. Later, Sergei helps Ivan and Katerina create weapons to beat Baba Yaga, and he even saves the king's life.