Reeri Yakseya or Reeri Yakka is a demon in Sinhalese folklore. It is believed to be the most cruel and powerful demon of all. Although Reeri Yakseya has the body of a human, his head is that of a monkey. His skin is fiery red in colour, and he rides a red bull. It is believed that he can afflict all kinds of illnesses on humans, but hemorrhages and blood diseases are especially attributed to him. A less popular belief is that these are not apparitions of the same demon but 18 individual demons who work together.