This is Kaiser's personal melee weapon, combined by mystical power of his guardian entity, SHAOQING, who is the gatekeeper of an endless winter afterlife dimension called the First Frost. The Lunar Diamond is one of many power gems, much like the Shadow Gem, only the Lunar Diamond has been Kaiser's power source since he discovered it in 2012. There is even a fraction of it in his heart.

(I couldn't find the origins of the real sword model, but I assumed it was a conquistador saber, or some sword from England or France. If you guys know the actual sword model, then thanks a bunch.)