Rune-lenses (魔導レンズ, Madō Renzu, Magic Lens) are a form of magic in Eiyuden Chronicle: Hundred Heroes. In Allraan, runes are affixed to "lenses", typically physical objects, which then allow the bearer to use the rune's power.
Rune-lenses are said to be the backbone of all power in Allraan and beyond. Lenses have different significance from nation to nation and culture to culture, but everywhere they exist, people have learned to harness their magical power.
In normal life, the power of rune-lenses can be used in many forms; to cast spells, use supernatural powers, or wield the lens symbolically by claiming a connection with the divine. In practical use, lenses are often crafted into weapons and accessories. However, the Galdean Empire has figured out how to amplify the lenses’ power further by placing them inside specially engineered rings called regules.
There are a great variety of rune-lenses and the most valuable are sometimes handed down through families. There are also some individuals who are born with them inside their bodies. They are not completely ubiquitous, however. Some people in the world prefer not to rely on them.