Ninja Gaiden II: The Dark Sword of Chaos is a side scrolling action game released in 1990 that is the sequel to the NES title Ninja Gaiden.
The game takes place a year after the events of Ninja Gaiden. With Ryu's triumph over the evil Jaquio, emperor Ashtar tries to rule the world using the dark sword of chaos. Ryu is recruited to defeat Ashtar.
Ninja Gaiden 2 plays similar to the original with a couple game play changes. Ryu can now easily move up and down walls that he's attached to. There's also a couple new power-ups including a clone power-up in which up to two clones will follow Ryu around and preform the same actions he does. Another new power-up is a fireball that shoots out in a downwards direction.
An update of the game was release as part of the SNES title
Ninja Gaiden Trilogy. Ninja Gaiden 2 is available on the Wii Virtual Console.