Poisons, Toxins and toxicity are gameplay elements present in Blood Omen: Legacy of Kain. Certain enemies possess toxic, poisonous or venomous attacks: if Kain is harmed by these creatures or drinks their blood, his Blood becomes green and begins to deplete much faster than usual. Toxidity was most commonly encountered in Dark Eden - most of the mutants therein possessed poisonous attacks and blood.
If Kain has enough blood to wait it out, the poisons will clear away on their own after a short time and his remaining blood will revert to red; otherwise, toxins could only be cured using Anti-toxins. Toxins and poisons are not present as a gameplay element in further games.