Erika —also known as "The Witch of Taboos" or “The Forbidden Witch”—is a magic researcher and enemy of the Goddess Vicius. She's famed around the continent as a grand magic user that possesses lost knowledge about many dark subjects deemed forbidden by the Goddess, such as curses and poisons.
Erika is quite guarded upon first meeting Touka and company. She is intelligent, crafty and prepared. Erika appears to love making things, especially outfits and clothing for herself and other ladies like Eve and Lis. She carries out experiments in her own laboratory. Erika even shores up and modifies artifacts in her inventory.

(Source: Wiki)