The cavern is located just northeast of Balka and is where Calegia's first ruler held a ceremony to declare the founding of the kingdom. In the story, it is revealed that the word mesechina means "light of the moon", which is supported by the fact that the cave glows as if it were being lit by the moon. The group first explores the dungeon in order to rescue the researcher Hack for Jibel in Balka, who thereafter agrees to show the group a secret entrance to Calegia Castle.
The group later revisits the cavern after a phenomenon known as the "impression" sweeps the kingdom, affecting all Gajuma, including Eugene Gallardo, who imprisons himself in the dungeon so that he will not be a danger to others. While Mao persistently remains with Eugene during the ordeal, the others venture to the eastern continent in order to obtain a "Pill of Serenity" that promises to pacify Eugene's heart. After retrieving the pill and returning to the cavern, the group is forced to fight Eugene before he calms entirely, returning to his normal self.
- Mesečina is a Serbo-Croatian word that translates to "moonlight", and this is directly referenced in the game.