"I may have been the last of the Head, but that doesn't mean that I won't put up a fight. Would you still have the power to face me, an Arbiter, though?~ "

Apart of the Head, an Arbiter. She is a powerhouse of a mage that can lob lethal magic through the use of Singularities. Along with that, she's also very durable. And the highest rank, above a Color Fixer.

…

You just stumbled into her path.