Erina the Legendary Hero is an Attack Type Story Hero.

Although it was not revealed until late Chapter 2 (Skyheim), Erina is actually the Demon King, who serves as the antagonist for the entirety of Chapter 1 (Kanterbury). Upon defeating the Demon King in area 15-4, it is heavily implied that the Demon King is a girl.

She appears to be very old, and knew Lilith the Demonic Princess when she was just a young girl.