Alchemy of Souls

Remarkably consistent — best ep S1E19

She was named Naksu because wherever she went, a trail of heads followed. She performs the alchemy of souls, magic that can change people's bodies and souls, which is forbidden in Daeho, and ends up being chased. Naksu hurriedly abandons her body and attempts the alchemy of souls on a woman passing by. Jang Wook, the son of the King of Daeho, realizes that Mudeok's soul has been changed and helps her. Jang Wook wants to learn Naksu's martial arts and become a sorcerer, and Naksu, in the body of Mudeok, stays by his side so she can recover her strength.