The Baneful Blood plays an important part in both the gameplay and story of the Onechanbara series. It is a cursed bloodline that attracts and reacts to tainted blood (usually that of the undead). When the degree of tainted blood splatter on the individual reaches a certain extent, the true potential of the Baneful Blood awakens in the form of a berserk state. In this condition, the individual's strength and speed increases tenfold, but this in turn gradually destroys their constitution.
Initially, this effect was permanent, and can only be counteracted by being purified using a Goddess Fragment or a praying to a Goddess Statue. This was changed in latter games where the status would eventually wane over time.
Aside from splatter sustained by attacking the undead, the individual can choose to intentionally increase the volume of tainted blood by using a Blood Cluster, an item usually obtained by disemboweling a Mudman.
Upon reaching berserk state , those with Baneful Blood make a last ditch effort to contain the reaction, but will inevitably succumb to it's effects. The resulting burst of power will destroy any undead within arm's length. The individual will then become enveloped in a hazy, dark-colored aura.
Aside from the strength and speed boost, individuals in a berserk state will be able to destroy Mudmen without using the disembowel move or Ecstasy Combos (or in Z Kagura, Vamp Skills). This state comes at a price: the violent movement of the blood takes a toll on their bodies, hence the loss of health. Moreover, the healing effect of Green Gems will have no effect. Only concentrated tainted blood in the form of Red Orbs or Blood Clusters can restore health.