OOPArts (発掘された超金属(オーパーツ) ōpātsu; English abbreviation for "Out-of-place-artifact", Japanese for "Excavated Super Metal") is the mysterious metal/stone that allows one to use magic/runes.
Though recently discovered, OOPArts have been around since ancient times and are believed to be linked to the supernatural phenomena involved in mythical legends; more likely, Norse Mythology. They are stones that were found in a cave on the island of Tsukuyomi-jima, when the come in contact with specific people they enter that person's body and manifest into weapons that person can use; magical weapons.
- OOPArts can be any color, from one color to multi-colored and can have decorations on them.
- If an OOPArts is damaged when fusing with a person, that person's magical weapon will be damaged of split.
- OOPArts can only fuse with certain people.