Ar Tonelico: Melody of Elemia

Viruses born in the Altar of Apostles have begun to appear, though normally not in physical form have now taken on the form of monsters and could destroy the world. In the upper levels of the Tower is a city called Platina where the Knights of Elemia reside; their job is to control virus outbreaks to preserve the tower. One such knight is Lyner Barsett, who will need to go on a quest to find the Hymn Crystal which can save the Tower of Ar tonelico and the whole world. (mobygames)