Haishera is the infamous "Demon God (Majin) of Earth".
Caring very little about things like delicacy, beauty and art, she enjoys good fights with strong opponents. She initially targets Celica Sylphil to obtain the body of the Goddess Astraea and temporarily succeeds in doing so. She became Kamigoroshi Haishera for a while.
Post Battle Goddess Episode Zero, she remains sealed in a blade Celica carries, and becomes his companion and advisor in that form. However she periodically has ceremonies (by means of having sex, of course) with Celica to power up the sword.