Agartha Reportアガルタの記録

A leatherbound book written in unsteady human language. It appears that the author believed to have found the mythological center of the earth, before succumbing to illness.
In-game description

How to get Agartha Report

Placed in or on the Deceased Explorer found inside a scene (building, ruin, camp and so on) (guaranteed)Where: Crystal Explorer's Camp [The Shimmering Frontier] (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.