Samurai Jack Season 3 Episode 11

The gods Odin, Ra, and Rama battle a great dark evil. One shard escapes and falls to primitive Earth, creating a vast black forest. Down through the millennia it spreads and kills until the period of feudal Japan. An emperor and his army set out to fight the evil with the aid of a mystical elixir. His army is wiped out but the emperor fires an arrow covered with the elixir into the heart of the darkness, but only sets it free and gives it voice and face: Aku. Aku imprisons the Emperor and wipes out his lands.