This dark lord of the sith was around during the time Palpatine first came into power over his republic/empire. He nearly ruined Darth Sidious's plans to take full control, as well as this seduction of Anikin to the dark side. Later Tal-Oc would fall to Vader's secret apprentice, after Vader himself could not take down Tal=Oc. Palpatine never got the answers to why his dark lord stayed off his radar or who he truly was...but their rivalry lasted decades, including a few confrontation that left both Sidious and his aprinatce Vader, scared and weak.