The Acolyte

The Acolyte is a worshipper of the Void. She actively chooses to remain in the abyss, believing the Pale King's actions will bring the void to reclaim Hallownest -- that is, that the world should be cloaked in darkness, and Hallownest is the first to be "cleansed".

She carved out the scar on her forehead and filled it with void from the abyss, and awaits the day that all of the void becomes united. When that day comes, she is prepared to sacrifice herself, become a shade permanently, and be one with the void.

Picrew location.