Once Anakin Skywalker now as a Sith Lord, Darth Vader was haunted by everyone that he had wronged in any way and this included Master Yoda who had previously mentored Anakin.
Once Anakin Skywalker now as a Sith Lord, Darth Vader was haunted by everyone that he had wronged in any way and this included Master Yoda who had previously mentored Anakin.