DARTH MAUL

Born on Iridonia, the Zabrak Maul was taken away from his family as a child by Darth Sidious who later revealed himself to be Palpatine. He was trained as a Sith Lord but when sent on his first mission to deal with two Jedi on Naboo he was supposedly killed by Obi-Wan Kenobi and sent, in two pieces, down a shaft.
Maul survived the fall using his Dark Side powers and escaped the planet before its destruction at the hands of the Mandalore ten years later. With the aid of cybernetic implants he was restored and went back to his master only to find he now had a new apprentice - Darth Vader.
After the death of Palpatine and Vader at Endor Maul started working for Thrawn who was now possessed with the old Emperor's essence. He had an opposition to the Chiss who he felt was not up to the position he was but continued working until a situation presented iteself.