Aurora

Aurora (アウロラ), also known as the Demon Diabolos, is a mysterious person from the distant past, regarded as the "Witch of Calamity" who plunged the world into chaos until she was sealed away by the Hero Olivier. In the present, the eponymous "Cult of Diablos" seems to be trying to harness her power for their own ends.

Appearance
Aurora has Violet hair, violet eyes, and she seems to have a mole under the right side of her mouth.

Personality
Not much is known about her past or motives, due to Aurora's amnesia. She is playful, humorous, and seems to be fond of Cid Kagenou.

Holy Ground Infiltration
Nothing is known about Aurora's past except that she was a war orphan. Very few members among the church know of her story. She first appears as a memory when Shadow is forced to participate in the goddess trial at Lindwurm. Shadow defeats Aurora and uses the ensuing chaos to flee the premises. Later, Cid Kagenou is surprised when a magical door crosses his path and stops him from going further. Cid opens the door and finds Aurora chained. He reluctantly saves Aurora who admits that she has been imprisoned for over a millennia. The two work together to escape the prison, which is actually a labyrinth of memories. They are assailed by Archbishop Nelson and the memory of Olivier, but Cid defeats them and destroys the core of the prison, which is actually Diabolos's hand. The prison is destroyed and Cid has a conversation with Aurora. Aurora tells him that she will cease to exist, but doesn't regret it at all. She also reveals that she was the one who summoned Cid and is glad to have met him. Before disappearing, Aurora tells Cid that if he ever finds the real her, he should kill her. Unknown to Cid, Aurora is the true identity of the great demon Diabolos.

Red Moon Incident
When Claire went to the top of the red tower of the Lawless City, to rescue her brother Cid, (unaware that he was not in danger), Claire was Gravity wounded by the Vampire Queen Elizabeth, and she began to experience a type of blood curse similar to "Demon Possession", while was unconscious while the others fighting, Aurora appeared to him in a sub-space inside Claire, starting to talk to Claire and helping her with her current state, giving her a spell that will allow her to control the 2 types of blood that flow and now inhabit her body, to later provide her support in combat, by borrowing Claire's body, Aurora joins the battle manifesting a slight change of character Claire's eyes color from black to violet, with a portion of her power, enough to slow down, damage, and push back the vampire queen Elizabeth, until Claire's body she has possessed reaches its limit due to the magical pressure exerted on it, but luck of all and as Aurora expected, Shadow appears to face and defeat Elizabeth once and for all,  but then at the end the battle the next day, Aurora disappears again, leaving the mark of the Spell on Claire, so that I can help in the near future.

Magic
While her full power remains unknown, Aurora is arguably the second-strongest character in the series after the Shadow. Even her projection was so powerful that Nelson believed that it could easily defeat the Shadow, and the Shadow himself noted that it paled in comparison to the real deal. When possessing Claire, though unable to bring out her full power, Aurora was able to considerably damage Elisabeth, something no one before that had even been capable of.

Her fighting style appears to revolve around summoning and telepathically manipulating several different weapons. Also, despite having been imprisoned for so long, her projection was capable of manifesting a magical door to summon the Shadow to her side. Aside from this, she can read magic runes.

Trivia

 * The name Aurora means "dawn" in Latin.