Mavic Chen

Mavic Chen was the Guardian of the Solar System around the turn of the 41st century and betrayer of the solar system to the Daleks.

Biography
Mavic Chen was corrupted by a lust for power, and willingly betrayed his own people. He allied himself with the Daleks (DW: Mission to the Unknown, The Daleks' Master Plan) and granted them the taranium they would need to complete their Time Destructor.

When the Doctor and his companions succeeded in stealing the taranium from the Daleks' base on Kembel, Chen at first recruited Space Security Service agent Sara Kingdom to help him. Chen had lied, telling her that her brother Bret Vyon, who was helping the Doctor, was a traitor. Sara believed Chen and killed her brother, but switched over to the Doctor's side upon learning the truth.

When the Doctor attempted to elude his enemies in his TARDIS, Chen joined the Daleks in their pursuit of them through the centuries. Chen was able to retrieve the taranium after the Daleks caught up with the Doctor in ancient Egypt. Chen and his allies returned to Kembel, where he was finally exterminated by the Daleks, having served out his usefulness.

By now insane, Chen proclaimed he was immortal even as the Daleks' disruptors fired upon him. The Daleks soon followed him in death, as the Doctor activated the Time Destructor himself and destroyed all life on Kembel. (DW: The Daleks' Master Plan)

Chen's Legacy
Despite Chen's betrayal of Earth and his extermination by the Daleks, he succeeded in founding a dynasty that controlled Earth and much of the galaxy for many centuries.