Maechen is a non-player character and scholar in Final Fantasy X and Final Fantasy X-2. He has a vast knowledge of the history and origins of all things related to Spira as well as its many cultures, and is infamous for his long-winded expositions, but much of Spira's history can only be learned from him.
Yuna and her guardians first meet Maechen on the Mi'ihen Highroad where he tells the tale of Lord Mi'ihen, the Crusaders, and the history of the Highroad. Thereafter he appears in many other locations, each time with a new story to tell.
On the Moonflow, Maechen explains about shoopufs and the Hypello. In Guadosalam, he tells about the Farplane and the pyreflies. On the Thunder Plains, Maechen tells the party about the plains and how the lightning towers were built. At the travel agency at Macalania, Maechen tells the lake is frozen due to the fayth in the nearby temple.
In the Calm Lands, Maechen explains the plains have been used by summoners as a battleground when fighting Sin and that's how the plains acquired their name. He eventually resides in Mt. Gagazet, where he reveals much of the lesser discussed history of Yevon.
After Yuna and her guardians fell Sin, Maechen in among the Besaid Village gathering around the bonfire with the Besaid Aurochs and Crusaders.