Black Beast

The legendary beast that threatened to cause much calamity before the current events of the game. It was confronted by the Six Heroes and sealed away. In actuality it is a combination of Ragna and Nu fusing together inside of the Cauldron (Ragna is its body, and Nu was its heart). In Continuum Shift it is revealed that the Black Beast was a failed product of Terumi in an attempt to create Kusanagi, the "Sword to Slay the Gods".