A Human shaped "Relic Eater," or Magical Heritage girl known as Malleus Maleficarum Type-Twilight "Mistilteinn." She can only transform into anything with a Blade.

Her Intristic Magic is known as "Twilight Enchantment" which lets her drain magic from allies or enemies and throw it somewhere else.
She becomes Kusanagi Takeru's Relic Eater.
She was previously Kusanagi's great descendant's, which was a female, Relic Eater during the Witch Hunt War.