Murasame and Masamune
The legendary twin katanas of the Lunarians, forged eons ago from an unknown Lunar ore and imbued with powerful Lunarian magic. They were believed to be so sharp that they could cut through anything, even adamantium.
In antiquity, the notorious Xsian pirate, Captain Kyrian Mizutsuki, stole them from a Lunarian temple and grew their legend right along with his own.