(Eh. It doesn't matter to me so much. i went and looked up the demon blade from yu yu hakushio. This can be an ethereal blade, maybe it manifests out of Mith's arm, er whatever. We'll nail it down later.)

Mithias didn't have time to scream as he was flash-incinerated once and again. Each time his body fell, it would reform of its own accord, making for an exquisite torture at Kami's hands. The torture was not so much of his body, but of his mind and soul, which persisted even through many deaths. The helplessness, the cruelty of the sadistic god, the mockery, and to know complete failure... Anguish turned to anger, and soon, without any planning or thought, Mithias' soul began to take shape. Rising in wisps and filaments out of his ashes, his own soul took on the form of the sword Tsukune had given him, forming the demonblade, a wraithblade made of spirit. 

Floating on its tip, Mithais' soul-sword glared at Kami, as if it had its own eyes. His lightning simply passed right through it, causing Mithias' husk of a body to burn and struggle to regenerate. Then, with all his fury, Mithias' soul aimed itself at Kami's heart and flew straight at it in a direct attack.