Mina Salem

The powerful being known as the  Witch of Witches, she had written the 9 Chapters of the Ilias Fragment where Ilia is the 3rd Chapter and Okto being the 8th Chapter. She seems to have red hair and wore a very large witch hat and know all types of magic, possibly even possessing all of them. Despite all her powers, she was defeated and murdered by the  Radix Astil  300 days before Arata and the Trinity Seven entered Dante's Gate. Radix Astil sealed seven of the 9 sisters of the Ilias Fragment in various levels of "hell." Okto wasn't sealed for some unknown reason and Ilia is with Arata while he trained during the 300 days. Radix Astil did this so she can see whether Arata can free the seven Ilias Fragment sisters to prove he is worthy to fight her master, Last Trinity. Following that, her body was promptly taken over by Albalisha.

Trivia

 * The nine chapters she wrote of the Ilias Fragment are the nine grimoires including Ilia and Okto.
 * All the grimoires she created are "legendary" class.