"Soul of the mind, key to life's ether.
Soul of the lost, withdrawn from its vessel.
Let strength be granted, so the world might be mended.
So the world might be mended."
The Maiden is Black is said to be one of the most powerful demons in existence and has the ability to modify the player's abilities in exchange for souls. Her eyes are occluded by wax, although this seems to have little impact on her ability to perceive the world around her.
The Maiden maintains the Nexus, keeping its candles lit and watching over the souls of the beings trapped within. She maintains a direct communion with the Old One, and is able to lull it back to sleep at the end of the game should the player choose the good ending.
The player may also choose to kill her and take her place at the Old One's side in the bad ending of the game, becoming a demon of immense power at the cost of the destruction of Boletaria, and eventually the rest of the world.