Yin

The Yin is a dark energy that is the collection of negative emotions and sins that people felt inside, and it plays a role in the 2002 videogame Shinobi.

The yin serves the hunger of Akujiki, the evil soul-eating sword. The more it kills, the more yin it consumes.

Hotsuma, now the leader of the Oboro Clan, forced to abate Akujiki's appetite for the yin. He uses the blade to destroy the Hellspawn and soon Hiruko who uses the yin of his victims and his puppets to gain power.

The Yin is the opposite of the Yang.