7th of the Fatui Harbingers. Before Nordcry, her only line was "Hmph, what a joke!" from 'A Winter Night's Lazzo,' leading to little speculation beyond her being sharp-tongued. However, she was revealed to have the least intimidating presence among the Harbingers despite her high pride. While prickly, she doesn't obsess over authority. She personally visited the Adventurers' Guild to warn the Traveler and Paimon, yet humored the Traveler's jokes about Katheryne by saying, "...Ad Astra Abyssosque. Welcome to Nordcry, the territory of the Fatui," showing a surprisingly human side. She takes great pride in her skills and was visibly frustrated when Columbina saved her just before Leryr could strike Pulonia. Contrary to her image as a fussy young lady, she has a combative side, confidently leading her modified Pulonia against Leryr. Her relationship with Columbina is complex; Columbina worries about Sandrone's irregular lifestyle and tells others that Sandrone is actually quite good at controlling her emotions.

2nd of the Fatui Harbingers. A narcissistic scientist with a cruel, cynical personality and a fanatical obsession with knowledge and experimentation. He hides his face behind a mask and treats humans and test subjects as mere tools. He is a villainous character who doesn't hesitate to commit inhumane acts, such as gaslighting those around him (like Scaramouche). His final words at death: "This damn world!!!"

Behind her innocent appearance lie many hints of overwhelming strength and madness. Though she looks like a frail girl, even high-ranking Harbingers are wary of her. Tartaglia advises avoiding a fight with her due to the threat he senses, and the Wanderer evaluates her as "extremely dull or insensitive, and not normal." She uses very polite and gentle speech, maintaining a calm and languid attitude regardless of the situation.