**The Great Sage** is a rare skill possessed by certain individuals, granting access to extensive knowledge of the world and its underlying laws. Users consult its repository to gain information on virtually any topic, including unknown subjects. Each use inflicts severe, debilitating headaches, though these can be mitigated through methods like kissing or acquiring a Headache Immunity skill. The Great Sage cannot access personal or private information, limiting its utility in specific contexts.

**Noir Stardia**, the primary known user, employs the skill early in his journey to locate a hidden dungeon. This leads him to encounter Olivia Servant, a legendary adventurer trapped inside, resulting in Noir acquiring additional skills from her. Despite its value for problem-solving, Noir uses the Great Sage sparingly due to the physical toll, preferring alternatives when possible.

**Merlin**, a historical sage, is another documented user. His application of the skill contributed to his renowned wisdom and understanding of the world’s mechanics, though he similarly endured the associated headaches. The effects and limitations for Merlin align entirely with Noir’s experience.

The Great Sage exhibits no additional background, development, or narrative evolution in available official media. Its role remains confined to facilitating Noir’s initial dungeon discovery and occasional information gathering, without deeper exploration of its origins or broader significance in the series’ universe.