Mysterious Doll Set謎の人形セット

A pair of green dolls wearing clothes, sitting together they look like great pals.
In-game description

How to get Mysterious Doll Set

Placed in or on the Chest found inside a scene (building, ruin, camp and so on) (guaranteed)Where: Mysterious Doll Set House [The Undergrounds] (1 per world)

Scene containers, dungeon placements, guaranteed drops and natural spawns are based on the Obtaining data of the Core Keeper Wiki (Fandom) (CC BY-SA 3.0), because these are not in the game files this site reads. Scene names are the wiki's English names.