Taint is when something has been polluted so that its outward appearance and reactions appear to be different than its [beginning] true nature. When a character acts excessively good, selfish, or evil it can leave a Taint upon their Aura – usually manifesting as a Marks of Impact.
A Tainting cannot cause death, it is not a true Disease or Poison or Toxin – it only appears so to those perceiving it. Taint can be of many impacts, but has Essence Taint, Divinity Taint; characters may be rewarded or penalized with taint.