Sandrone, also known by her codename "Marionette,"[1] was the Seventh of the Eleven Fatui Harbingers and a member of the Adventurers' Guild. She was stationed in Nod-Krai to oversee the Kuuvahki Experimental Design Bureau.

She was created by Alain Guillotin in the image of his deceased sister, Mary-Ann Guillotin, and keeps Pulonia, his final creation, as her constant companion following Guillotin's death.[8]

Sandrone is a young, pale-skinned woman of medium height with blue-grey eyes. She has beige-coloured hair tied back in a braided bun with two long strands framing her face.

She wears a long white dress with red ruffles and a black corset with a triquetra symbol in the middle, with ruby-red gemstones in the spaces. Her dress features a black collar with gold accents and a pear-cut ruby-red gem, and long white sleeves, with short, dark, puffy sleeves over them. Her gloves are white and form a V-shape at the wrist. She wears white stockings with black heels. Upon her head is a white, black, and gold bonnet with red lacing and black bows on the sides. A puppet wind-up key protrudes from her back.