Hoarfrost

Hoarfrost (白死) was the name of a sword wielded by Guren Ichinose.

Story
According to one of the many tales about the blade, it cut down a thousand demons in a row without getting a single nick.

Events of 2012
Kureto Hīragi gives this sword to Guren after he swears loyalty to him. It vibrates and emits a high pitched ring when Guren drew it from its sheath and was then filled with the desire for slaughter and bloodshed.