Pandora is the Witch of Vainglory who has a mysterious relationship with the Witch Cult. Due to her seeming command over the Cult, she can actively be described as one of the main antagonists of Re:Zero.

She played a part in several atrocities throughout history, including the attack on Elior Forest as well as the death of Theresia van Astrea at the hands of the Hakugei.

Pandora appears as young girl and has long, transparent platinum hair with dark blue eyes, and long eyelashes. She is beautiful enough to be said to make other tremble with her beauty and that even God would hesitate to touch her. Humans have an ideal of beauty, and Pandora is the answer to that beauty. Also, if beauty could kill, Pandora would be that beauty.

At first glance, Pandora is dignified and graceful, with a generally calm demeanor. This calm exterior hid an extremely selfish and sociopathic personality, whom was willing to do anything to achieve her goals.

Pandora's origins and goals are shrouded with mystery, as history has no mention of her. At an unknown point in time, she became the Witch of Vainglory, and set out on a path of destruction.

(Source: Re:Zero Wikia)